1  /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   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
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  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 "classfile/classLoaderData.inline.hpp"
  50 #include "classfile/classLoaderDataGraph.inline.hpp"
  51 #include "classfile/dictionary.hpp"
  52 #include "classfile/javaClasses.inline.hpp"
  53 #include "classfile/moduleEntry.hpp"
  54 #include "classfile/packageEntry.hpp"
  55 #include "classfile/symbolTable.hpp"
  56 #include "classfile/systemDictionary.hpp"
  57 #include "classfile/systemDictionaryShared.hpp"
  58 #include "classfile/vmClasses.hpp"
  59 #include "logging/log.hpp"
  60 #include "logging/logStream.hpp"
  61 #include "memory/allocation.inline.hpp"
  62 #include "memory/classLoaderMetaspace.hpp"
  63 #include "memory/metadataFactory.hpp"
  64 #include "memory/metaspace.hpp"
  65 #include "memory/resourceArea.hpp"
  66 #include "memory/universe.hpp"
  67 #include "oops/access.inline.hpp"
  68 #include "oops/inlineKlass.inline.hpp"
  69 #include "oops/klass.inline.hpp"
  70 #include "oops/oop.inline.hpp"
  71 #include "oops/oopHandle.inline.hpp"
  72 #include "oops/verifyOopClosure.hpp"
  73 #include "oops/weakHandle.inline.hpp"
  74 #include "runtime/arguments.hpp"
  75 #include "runtime/atomic.hpp"
  76 #include "runtime/handles.inline.hpp"
  77 #include "runtime/mutex.hpp"
  78 #include "runtime/safepoint.hpp"
  79 #include "utilities/growableArray.hpp"
  80 #include "utilities/macros.hpp"
  81 #include "utilities/ostream.hpp"
  82 
  83 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = nullptr;
  84 
  85 void ClassLoaderData::init_null_class_loader_data() {
  86   assert(_the_null_class_loader_data == nullptr, "cannot initialize twice");
  87   assert(ClassLoaderDataGraph::_head == nullptr, "cannot initialize twice");
  88 
  89   _the_null_class_loader_data = new ClassLoaderData(Handle(), false);
  90   ClassLoaderDataGraph::_head = _the_null_class_loader_data;
  91   assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
  92 
  93   LogTarget(Trace, class, loader, data) lt;
  94   if (lt.is_enabled()) {
  95     ResourceMark rm;
  96     LogStream ls(lt);
  97     ls.print("create ");
  98     _the_null_class_loader_data->print_value_on(&ls);
  99     ls.cr();
 100   }
 101 }
 102 
 103 // Obtain and set the class loader's name within the ClassLoaderData so
 104 // it will be available for error messages, logging, JFR, etc.  The name
 105 // and klass are available after the class_loader oop is no longer alive,
 106 // during unloading.
 107 void ClassLoaderData::initialize_name(Handle class_loader) {
 108   ResourceMark rm;
 109 
 110   // Obtain the class loader's name.  If the class loader's name was not
 111   // explicitly set during construction, the CLD's _name field will be null.
 112   oop cl_name = java_lang_ClassLoader::name(class_loader());
 113   if (cl_name != nullptr) {
 114     const char* cl_instance_name = java_lang_String::as_utf8_string(cl_name);
 115 
 116     if (cl_instance_name != nullptr && cl_instance_name[0] != '\0') {
 117       _name = SymbolTable::new_symbol(cl_instance_name);
 118     }
 119   }
 120 
 121   // Obtain the class loader's name and identity hash.  If the class loader's
 122   // name was not explicitly set during construction, the class loader's name and id
 123   // will be set to the qualified class name of the class loader along with its
 124   // identity hash.
 125   // If for some reason the ClassLoader's constructor has not been run, instead of
 126   // leaving the _name_and_id field null, fall back to the external qualified class
 127   // name.  Thus CLD's _name_and_id field should never have a null value.
 128   oop cl_name_and_id = java_lang_ClassLoader::nameAndId(class_loader());
 129   const char* cl_instance_name_and_id =
 130                   (cl_name_and_id == nullptr) ? _class_loader_klass->external_name() :
 131                                              java_lang_String::as_utf8_string(cl_name_and_id);
 132   assert(cl_instance_name_and_id != nullptr && cl_instance_name_and_id[0] != '\0', "class loader has no name and id");
 133   _name_and_id = SymbolTable::new_symbol(cl_instance_name_and_id);
 134 }
 135 
 136 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder) :
 137   _metaspace(nullptr),
 138   _metaspace_lock(new Mutex(Mutex::nosafepoint-2, "MetaspaceAllocation_lock")),
 139   _unloading(false), _has_class_mirror_holder(has_class_mirror_holder),
 140   _modified_oops(true),
 141   // A non-strong hidden class loader data doesn't have anything to keep
 142   // it from being unloaded during parsing of the non-strong hidden class.
 143   // The null-class-loader should always be kept alive.
 144   _keep_alive_ref_count((has_class_mirror_holder || h_class_loader.is_null()) ? 1 : 0),
 145   _claim(0),
 146   _handles(),
 147   _klasses(nullptr), _packages(nullptr), _modules(nullptr), _unnamed_module(nullptr), _dictionary(nullptr),
 148   _jmethod_ids(nullptr),
 149   _deallocate_list(nullptr),
 150   _next(nullptr),
 151   _unloading_next(nullptr),
 152   _class_loader_klass(nullptr), _name(nullptr), _name_and_id(nullptr) {
 153 
 154   if (!h_class_loader.is_null()) {
 155     _class_loader = _handles.add(h_class_loader());
 156     _class_loader_klass = h_class_loader->klass();
 157     initialize_name(h_class_loader);
 158   }
 159 
 160   if (!has_class_mirror_holder) {
 161     // The holder is initialized later for non-strong hidden classes,
 162     // and before calling anything that call class_loader().
 163     initialize_holder(h_class_loader);
 164 
 165     // A ClassLoaderData created solely for a non-strong hidden class should never
 166     // have a ModuleEntryTable or PackageEntryTable created for it.
 167     _packages = new PackageEntryTable();
 168     if (h_class_loader.is_null()) {
 169       // Create unnamed module for boot loader
 170       _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
 171     } else {
 172       // Create unnamed module for all other loaders
 173       _unnamed_module = ModuleEntry::create_unnamed_module(this);
 174     }
 175     _dictionary = create_dictionary();
 176   }
 177 
 178   NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
 179 
 180   JFR_ONLY(INIT_ID(this);)
 181 }
 182 
 183 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
 184   Chunk* c = _head;
 185   while (c != nullptr) {
 186     Chunk* next = c->_next;
 187     delete c;
 188     c = next;
 189   }
 190 }
 191 
 192 OopHandle ClassLoaderData::ChunkedHandleList::add(oop o) {
 193   if (_head == nullptr || _head->_size == Chunk::CAPACITY) {
 194     Chunk* next = new Chunk(_head);
 195     Atomic::release_store(&_head, next);
 196   }
 197   oop* handle = &_head->_data[_head->_size];
 198   NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, o);
 199   Atomic::release_store(&_head->_size, _head->_size + 1);
 200   return OopHandle(handle);
 201 }
 202 
 203 int ClassLoaderData::ChunkedHandleList::count() const {
 204   int count = 0;
 205   Chunk* chunk = Atomic::load_acquire(&_head);
 206   while (chunk != nullptr) {
 207     count += Atomic::load(&chunk->_size);
 208     chunk = chunk->_next;
 209   }
 210   return count;
 211 }
 212 
 213 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
 214   for (juint i = 0; i < size; i++) {
 215     f->do_oop(&c->_data[i]);
 216   }
 217 }
 218 
 219 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
 220   Chunk* head = Atomic::load_acquire(&_head);
 221   if (head != nullptr) {
 222     // Must be careful when reading size of head
 223     oops_do_chunk(f, head, Atomic::load_acquire(&head->_size));
 224     for (Chunk* c = head->_next; c != nullptr; c = c->_next) {
 225       oops_do_chunk(f, c, c->_size);
 226     }
 227   }
 228 }
 229 
 230 class VerifyContainsOopClosure : public OopClosure {
 231   oop  _target;
 232   bool _found;
 233 
 234  public:
 235   VerifyContainsOopClosure(oop target) : _target(target), _found(false) {}
 236 
 237   void do_oop(oop* p) {
 238     if (p != nullptr && NativeAccess<AS_NO_KEEPALIVE>::oop_load(p) == _target) {
 239       _found = true;
 240     }
 241   }
 242 
 243   void do_oop(narrowOop* p) {
 244     // The ChunkedHandleList should not contain any narrowOop
 245     ShouldNotReachHere();
 246   }
 247 
 248   bool found() const {
 249     return _found;
 250   }
 251 };
 252 
 253 bool ClassLoaderData::ChunkedHandleList::contains(oop p) {
 254   VerifyContainsOopClosure cl(p);
 255   oops_do(&cl);
 256   return cl.found();
 257 }
 258 
 259 #ifndef PRODUCT
 260 bool ClassLoaderData::ChunkedHandleList::owner_of(oop* oop_handle) {
 261   Chunk* chunk = Atomic::load_acquire(&_head);
 262   while (chunk != nullptr) {
 263     if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[Atomic::load(&chunk->_size)])) {
 264       return true;
 265     }
 266     chunk = chunk->_next;
 267   }
 268   return false;
 269 }
 270 #endif // PRODUCT
 271 
 272 void ClassLoaderData::clear_claim(int claim) {
 273   for (;;) {
 274     int old_claim = Atomic::load(&_claim);
 275     if ((old_claim & claim) == 0) {
 276       return;
 277     }
 278     int new_claim = old_claim & ~claim;
 279     if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
 280       return;
 281     }
 282   }
 283 }
 284 
 285 #ifdef ASSERT
 286 void ClassLoaderData::verify_not_claimed(int claim) {
 287   assert((_claim & claim) == 0, "Found claim: %d bits in _claim: %d", claim, _claim);
 288 }
 289 #endif
 290 
 291 bool ClassLoaderData::try_claim(int claim) {
 292   for (;;) {
 293     int old_claim = Atomic::load(&_claim);
 294     if ((old_claim & claim) == claim) {
 295       return false;
 296     }
 297     int new_claim = old_claim | claim;
 298     if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
 299       return true;
 300     }
 301   }
 302 }
 303 
 304 void ClassLoaderData::demote_strong_roots() {
 305   // The oop handle area contains strong roots that the GC traces from. We are about
 306   // to demote them to strong native oops that the GC does *not* trace from. Conceptually,
 307   // we are retiring a rather normal strong root, and creating a strong non-root handle,
 308   // which happens to reuse the same address as the normal strong root had.
 309   // Unless we invoke the right barriers, the GC might not notice that a strong root
 310   // has been pulled from the system, and is left unprocessed by the GC. There can be
 311   // several consequences:
 312   // 1. A concurrently marking snapshot-at-the-beginning GC might assume that the contents
 313   //    of all strong roots get processed by the GC in order to keep them alive. Without
 314   //    barriers, some objects might not be kept alive.
 315   // 2. A concurrently relocating GC might assume that after moving an object, a subsequent
 316   //    tracing from all roots can fix all the pointers in the system, which doesn't play
 317   //    well with roots racingly being pulled.
 318   // 3. A concurrent GC using colored pointers, might assume that tracing the object graph
 319   //    from roots results in all pointers getting some particular color, which also doesn't
 320   //    play well with roots being pulled out from the system concurrently.
 321 
 322   class TransitionRootsOopClosure : public OopClosure {
 323   public:
 324     virtual void do_oop(oop* p) {
 325       // By loading the strong root with the access API, we can use the right barriers to
 326       // store the oop as a strong non-root handle, that happens to reuse the same memory
 327       // address as the strong root. The barriered store ensures that:
 328       // 1. The concurrent SATB marking properties are satisfied as the store will keep
 329       //    the oop alive.
 330       // 2. The concurrent object movement properties are satisfied as we store the address
 331       //    of the new location of the object, if any.
 332       // 3. The colors if any will be stored as the new good colors.
 333       oop obj = NativeAccess<>::oop_load(p); // Load the strong root
 334       NativeAccess<>::oop_store(p, obj); // Store the strong non-root
 335     }
 336 
 337     virtual void do_oop(narrowOop* p) {
 338       ShouldNotReachHere();
 339     }
 340   } cl;
 341   oops_do(&cl, ClassLoaderData::_claim_none, false /* clear_mod_oops */);
 342 }
 343 
 344 // Non-strong hidden classes have their own ClassLoaderData that is marked to keep alive
 345 // while the class is being parsed, and if the class appears on the module fixup list.
 346 // Due to the uniqueness that no other class shares the hidden class' name or
 347 // ClassLoaderData, no other non-GC thread has knowledge of the hidden class while
 348 // it is being defined, therefore _keep_alive_ref_count is not volatile or atomic.
 349 void ClassLoaderData::inc_keep_alive_ref_count() {
 350   if (has_class_mirror_holder()) {
 351     assert(_keep_alive_ref_count > 0, "Invalid keep alive increment count");
 352     _keep_alive_ref_count++;
 353   }
 354 }
 355 
 356 void ClassLoaderData::dec_keep_alive_ref_count() {
 357   if (has_class_mirror_holder()) {
 358     assert(_keep_alive_ref_count > 0, "Invalid keep alive decrement count");
 359     if (_keep_alive_ref_count == 1) {
 360       // When the keep_alive_ref_count counter is 1, the oop handle area is a strong root,
 361       // acting as input to the GC tracing. Such strong roots are part of the
 362       // snapshot-at-the-beginning, and can not just be pulled out from the
 363       // system when concurrent GCs are running at the same time, without
 364       // invoking the right barriers.
 365       demote_strong_roots();
 366     }
 367     _keep_alive_ref_count--;
 368   }
 369 }
 370 
 371 void ClassLoaderData::oops_do(OopClosure* f, int claim_value, bool clear_mod_oops) {
 372   if (claim_value != ClassLoaderData::_claim_none && !try_claim(claim_value)) {
 373     return;
 374   }
 375 
 376   // Only clear modified_oops after the ClassLoaderData is claimed.
 377   if (clear_mod_oops) {
 378     clear_modified_oops();
 379   }
 380 
 381   _handles.oops_do(f);
 382 }
 383 
 384 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
 385   // Lock-free access requires load_acquire
 386   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 387     klass_closure->do_klass(k);
 388     assert(k != k->next_link(), "no loops!");
 389   }
 390 }
 391 
 392 void ClassLoaderData::classes_do(void f(Klass * const)) {
 393   // Lock-free access requires load_acquire
 394   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 395     f(k);
 396     assert(k != k->next_link(), "no loops!");
 397   }
 398 }
 399 
 400 void ClassLoaderData::methods_do(void f(Method*)) {
 401   // Lock-free access requires load_acquire
 402   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 403     if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
 404       InstanceKlass::cast(k)->methods_do(f);
 405     }
 406   }
 407 }
 408 
 409 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
 410   // Lock-free access requires load_acquire
 411   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 412     // Filter out InstanceKlasses (or their ObjArrayKlasses) that have not entered the
 413     // loaded state.
 414     if (k->is_instance_klass()) {
 415       if (!InstanceKlass::cast(k)->is_loaded()) {
 416         continue;
 417       }
 418     } else if (k->is_shared() && k->is_objArray_klass()) {
 419       Klass* bottom = ObjArrayKlass::cast(k)->bottom_klass();
 420       if (bottom->is_instance_klass() && !InstanceKlass::cast(bottom)->is_loaded()) {
 421         // This could happen if <bottom> is a shared class that has been restored
 422         // but is not yet marked as loaded. All archived array classes of the
 423         // bottom class are already restored and placed in the _klasses list.
 424         continue;
 425       }
 426     }
 427 
 428 #ifdef ASSERT
 429     oop m = k->java_mirror();
 430     assert(m != nullptr, "nullptr mirror");
 431     assert(m->is_a(vmClasses::Class_klass()), "invalid mirror");
 432 #endif
 433     klass_closure->do_klass(k);
 434   }
 435 }
 436 
 437 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
 438   // Lock-free access requires load_acquire
 439   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 440     if (k->is_instance_klass()) {
 441       f(InstanceKlass::cast(k));
 442     }
 443     assert(k != k->next_link(), "no loops!");
 444   }
 445 }
 446 
 447 void ClassLoaderData::inline_classes_do(void f(InlineKlass*)) {
 448   // Lock-free access requires load_acquire
 449   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 450     if (k->is_inline_klass()) {
 451       f(InlineKlass::cast(k));
 452     }
 453     assert(k != k->next_link(), "no loops!");
 454   }
 455 }
 456 
 457 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
 458   assert_locked_or_safepoint(Module_lock);
 459   if (_unnamed_module != nullptr) {
 460     f(_unnamed_module);
 461   }
 462   if (_modules != nullptr) {
 463     _modules->modules_do(f);
 464   }
 465 }
 466 
 467 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
 468   assert_locked_or_safepoint(Module_lock);
 469   if (_packages != nullptr) {
 470     _packages->packages_do(f);
 471   }
 472 }
 473 
 474 void ClassLoaderData::record_dependency(const Klass* k) {
 475   assert(k != nullptr, "invariant");
 476 
 477   ClassLoaderData * const from_cld = this;
 478   ClassLoaderData * const to_cld = k->class_loader_data();
 479 
 480   // Do not need to record dependency if the dependency is to a class whose
 481   // class loader data is never freed.  (i.e. the dependency's class loader
 482   // is one of the three builtin class loaders and the dependency's class
 483   // loader data has a ClassLoader holder, not a Class holder.)
 484   if (to_cld->is_permanent_class_loader_data()) {
 485     return;
 486   }
 487 
 488   oop to;
 489   if (to_cld->has_class_mirror_holder()) {
 490     // Just return if a non-strong hidden class class is attempting to record a dependency
 491     // to itself.  (Note that every non-strong hidden class has its own unique class
 492     // loader data.)
 493     if (to_cld == from_cld) {
 494       return;
 495     }
 496     // Hidden class dependencies are through the mirror.
 497     to = k->java_mirror();
 498   } else {
 499     to = to_cld->class_loader();
 500     oop from = from_cld->class_loader();
 501 
 502     // Just return if this dependency is to a class with the same or a parent
 503     // class_loader.
 504     if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {
 505       return; // this class loader is in the parent list, no need to add it.
 506     }
 507   }
 508 
 509   // It's a dependency we won't find through GC, add it.
 510   if (!_handles.contains(to)) {
 511     NOT_PRODUCT(Atomic::inc(&_dependency_count));
 512     LogTarget(Trace, class, loader, data) lt;
 513     if (lt.is_enabled()) {
 514       ResourceMark rm;
 515       LogStream ls(lt);
 516       ls.print("adding dependency from ");
 517       print_value_on(&ls);
 518       ls.print(" to ");
 519       to_cld->print_value_on(&ls);
 520       ls.cr();
 521     }
 522     Handle dependency(Thread::current(), to);
 523     add_handle(dependency);
 524     // Added a potentially young gen oop to the ClassLoaderData
 525     record_modified_oops();
 526   }
 527 }
 528 
 529 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
 530   {
 531     MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 532     Klass* old_value = _klasses;
 533     k->set_next_link(old_value);
 534     // Link the new item into the list, making sure the linked class is stable
 535     // since the list can be walked without a lock
 536     Atomic::release_store(&_klasses, k);
 537     if (k->is_array_klass()) {
 538       ClassLoaderDataGraph::inc_array_classes(1);
 539     } else {
 540       ClassLoaderDataGraph::inc_instance_classes(1);
 541     }
 542   }
 543 
 544   if (publicize) {
 545     LogTarget(Trace, class, loader, data) lt;
 546     if (lt.is_enabled()) {
 547       ResourceMark rm;
 548       LogStream ls(lt);
 549       ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
 550       print_value_on(&ls);
 551       ls.cr();
 552     }
 553   }
 554 }
 555 
 556 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
 557   if (loader_or_mirror() != nullptr) {
 558     assert(_holder.is_null(), "never replace holders");
 559     _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror);
 560   }
 561 }
 562 
 563 // Remove a klass from the _klasses list for scratch_class during redefinition
 564 // or parsed class in the case of an error.
 565 void ClassLoaderData::remove_class(Klass* scratch_class) {
 566   assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
 567 
 568   Klass* prev = nullptr;
 569   for (Klass* k = _klasses; k != nullptr; k = k->next_link()) {
 570     if (k == scratch_class) {
 571       if (prev == nullptr) {
 572         _klasses = k->next_link();
 573       } else {
 574         Klass* next = k->next_link();
 575         prev->set_next_link(next);
 576       }
 577 
 578       if (k->is_array_klass()) {
 579         ClassLoaderDataGraph::dec_array_classes(1);
 580       } else {
 581         ClassLoaderDataGraph::dec_instance_classes(1);
 582       }
 583 
 584       return;
 585     }
 586     prev = k;
 587     assert(k != k->next_link(), "no loops!");
 588   }
 589   ShouldNotReachHere();   // should have found this class!!
 590 }
 591 
 592 void ClassLoaderData::unload() {
 593   _unloading = true;
 594 
 595   LogTarget(Trace, class, loader, data) lt;
 596   if (lt.is_enabled()) {
 597     ResourceMark rm;
 598     LogStream ls(lt);
 599     ls.print("unload");
 600     print_value_on(&ls);
 601     ls.cr();
 602   }
 603 
 604   // Some items on the _deallocate_list need to free their C heap structures
 605   // if they are not already on the _klasses list.
 606   free_deallocate_list_C_heap_structures();
 607 
 608   inline_classes_do(InlineKlass::cleanup);
 609 
 610   // Clean up class dependencies and tell serviceability tools
 611   // these classes are unloading.  This must be called
 612   // after erroneous classes are released.
 613   classes_do(InstanceKlass::unload_class);
 614 
 615   // Method::clear_jmethod_ids only sets the jmethod_ids to null without
 616   // releasing the memory for related JNIMethodBlocks and JNIMethodBlockNodes.
 617   // This is done intentionally because native code (e.g. JVMTI agent) holding
 618   // jmethod_ids may access them after the associated classes and class loader
 619   // are unloaded. The Java Native Interface Specification says "method ID
 620   // does not prevent the VM from unloading the class from which the ID has
 621   // been derived. After the class is unloaded, the method or field ID becomes
 622   // invalid". In real world usages, the native code may rely on jmethod_ids
 623   // being null after class unloading. Hence, it is unsafe to free the memory
 624   // from the VM side without knowing when native code is going to stop using
 625   // them.
 626   if (_jmethod_ids != nullptr) {
 627     Method::clear_jmethod_ids(this);
 628   }
 629 }
 630 
 631 ModuleEntryTable* ClassLoaderData::modules() {
 632   // Lazily create the module entry table at first request.
 633   // Lock-free access requires load_acquire.
 634   ModuleEntryTable* modules = Atomic::load_acquire(&_modules);
 635   if (modules == nullptr) {
 636     MutexLocker m1(Module_lock);
 637     // Check if _modules got allocated while we were waiting for this lock.
 638     if ((modules = _modules) == nullptr) {
 639       modules = new ModuleEntryTable();
 640 
 641       {
 642         MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 643         // Ensure _modules is stable, since it is examined without a lock
 644         Atomic::release_store(&_modules, modules);
 645       }
 646     }
 647   }
 648   return modules;
 649 }
 650 
 651 const int _boot_loader_dictionary_size    = 1009;
 652 const int _default_loader_dictionary_size = 107;
 653 
 654 Dictionary* ClassLoaderData::create_dictionary() {
 655   assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary");
 656   int size;
 657   if (_the_null_class_loader_data == nullptr) {
 658     size = _boot_loader_dictionary_size;
 659   } else if (is_system_class_loader_data()) {
 660     size = _boot_loader_dictionary_size;
 661   } else {
 662     size = _default_loader_dictionary_size;
 663   }
 664   return new Dictionary(this, size);
 665 }
 666 
 667 // Tell the GC to keep this klass alive. Needed while iterating ClassLoaderDataGraph,
 668 // and any runtime code that uses klasses.
 669 oop ClassLoaderData::holder() const {
 670   // A klass that was previously considered dead can be looked up in the
 671   // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
 672   // or a reachable object making it alive again. The SATB part of G1 needs
 673   // to get notified about this potential resurrection, otherwise the marking
 674   // might not find the object.
 675   if (!_holder.is_null()) {  // null class_loader
 676     return _holder.resolve();
 677   } else {
 678     return nullptr;
 679   }
 680 }
 681 
 682 // Let the GC read the holder without keeping it alive.
 683 oop ClassLoaderData::holder_no_keepalive() const {
 684   if (!_holder.is_null()) {  // null class_loader
 685     return _holder.peek();
 686   } else {
 687     return nullptr;
 688   }
 689 }
 690 
 691 // Unloading support
 692 bool ClassLoaderData::is_alive() const {
 693   bool alive = (_keep_alive_ref_count > 0) // null class loader and incomplete non-strong hidden class.
 694       || (_holder.peek() != nullptr);      // and not cleaned by the GC weak handle processing.
 695 
 696   return alive;
 697 }
 698 
 699 class ReleaseKlassClosure: public KlassClosure {
 700 private:
 701   size_t  _instance_class_released;
 702   size_t  _array_class_released;
 703 public:
 704   ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
 705 
 706   size_t instance_class_released() const { return _instance_class_released; }
 707   size_t array_class_released()    const { return _array_class_released;    }
 708 
 709   void do_klass(Klass* k) {
 710     if (k->is_array_klass()) {
 711       _array_class_released ++;
 712     } else {
 713       assert(k->is_instance_klass(), "Must be");
 714       _instance_class_released ++;
 715     }
 716     k->release_C_heap_structures();
 717   }
 718 };
 719 
 720 ClassLoaderData::~ClassLoaderData() {
 721   // Release C heap structures for all the classes.
 722   ReleaseKlassClosure cl;
 723   classes_do(&cl);
 724 
 725   ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
 726   ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
 727 
 728   // Release the WeakHandle
 729   _holder.release(Universe::vm_weak());
 730 
 731   // Release C heap allocated hashtable for all the packages.
 732   if (_packages != nullptr) {
 733     // Destroy the table itself
 734     delete _packages;
 735     _packages = nullptr;
 736   }
 737 
 738   // Release C heap allocated hashtable for all the modules.
 739   if (_modules != nullptr) {
 740     // Destroy the table itself
 741     delete _modules;
 742     _modules = nullptr;
 743   }
 744 
 745   // Release C heap allocated hashtable for the dictionary
 746   if (_dictionary != nullptr) {
 747     // Destroy the table itself
 748     delete _dictionary;
 749     _dictionary = nullptr;
 750   }
 751 
 752   if (_unnamed_module != nullptr) {
 753     delete _unnamed_module;
 754     _unnamed_module = nullptr;
 755   }
 756 
 757   // release the metaspace
 758   ClassLoaderMetaspace *m = _metaspace;
 759   if (m != nullptr) {
 760     _metaspace = nullptr;
 761     delete m;
 762   }
 763 
 764   // Delete lock
 765   delete _metaspace_lock;
 766 
 767   // Delete free list
 768   if (_deallocate_list != nullptr) {
 769     delete _deallocate_list;
 770   }
 771 
 772   // Decrement refcounts of Symbols if created.
 773   if (_name != nullptr) {
 774     _name->decrement_refcount();
 775   }
 776   if (_name_and_id != nullptr) {
 777     _name_and_id->decrement_refcount();
 778   }
 779 }
 780 
 781 // Returns true if this class loader data is for the app class loader
 782 // or a user defined system class loader.  (Note that the class loader
 783 // data may have a Class holder.)
 784 bool ClassLoaderData::is_system_class_loader_data() const {
 785   return SystemDictionary::is_system_class_loader(class_loader());
 786 }
 787 
 788 // Returns true if this class loader data is for the platform class loader.
 789 // (Note that the class loader data may have a Class holder.)
 790 bool ClassLoaderData::is_platform_class_loader_data() const {
 791   return SystemDictionary::is_platform_class_loader(class_loader());
 792 }
 793 
 794 // Returns true if the class loader for this class loader data is one of
 795 // the 3 builtin (boot application/system or platform) class loaders,
 796 // including a user-defined system class loader.  Note that if the class
 797 // loader data is for a non-strong hidden class then it may
 798 // get freed by a GC even if its class loader is one of these loaders.
 799 bool ClassLoaderData::is_builtin_class_loader_data() const {
 800   return (is_boot_class_loader_data() ||
 801           SystemDictionary::is_system_class_loader(class_loader()) ||
 802           SystemDictionary::is_platform_class_loader(class_loader()));
 803 }
 804 
 805 // Returns true if this class loader data is a class loader data
 806 // that is not ever freed by a GC.  It must be the CLD for one of the builtin
 807 // class loaders and not the CLD for a non-strong hidden class.
 808 bool ClassLoaderData::is_permanent_class_loader_data() const {
 809   return is_builtin_class_loader_data() && !has_class_mirror_holder();
 810 }
 811 
 812 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
 813   // If the metaspace has not been allocated, create a new one.  Might want
 814   // to create smaller arena for Reflection class loaders also.
 815   // The reason for the delayed allocation is because some class loaders are
 816   // simply for delegating with no metadata of their own.
 817   // Lock-free access requires load_acquire.
 818   ClassLoaderMetaspace* metaspace = Atomic::load_acquire(&_metaspace);
 819   if (metaspace == nullptr) {
 820     MutexLocker ml(_metaspace_lock,  Mutex::_no_safepoint_check_flag);
 821     // Check if _metaspace got allocated while we were waiting for this lock.
 822     if ((metaspace = _metaspace) == nullptr) {
 823       if (this == the_null_class_loader_data()) {
 824         assert (class_loader() == nullptr, "Must be");
 825         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
 826       } else if (has_class_mirror_holder()) {
 827         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType);
 828       } else {
 829         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
 830       }
 831       // Ensure _metaspace is stable, since it is examined without a lock
 832       Atomic::release_store(&_metaspace, metaspace);
 833     }
 834   }
 835   return metaspace;
 836 }
 837 
 838 OopHandle ClassLoaderData::add_handle(Handle h) {
 839   MutexLocker ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 840   record_modified_oops();
 841   return _handles.add(h());
 842 }
 843 
 844 void ClassLoaderData::remove_handle(OopHandle h) {
 845   assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
 846   if (!h.is_empty()) {
 847     assert(_handles.owner_of(h.ptr_raw()),
 848            "Got unexpected handle " PTR_FORMAT, p2i(h.ptr_raw()));
 849     h.replace(oop(nullptr));
 850   }
 851 }
 852 
 853 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
 854   MutexLocker ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 855   if (dest.resolve() != nullptr) {
 856     return;
 857   } else {
 858     record_modified_oops();
 859     dest = _handles.add(h());
 860   }
 861 }
 862 
 863 // Add this metadata pointer to be freed when it's safe.  This is only during
 864 // a safepoint which checks if handles point to this metadata field.
 865 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
 866   // Metadata in shared region isn't deleted.
 867   if (!m->is_shared()) {
 868     MutexLocker ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 869     if (_deallocate_list == nullptr) {
 870       _deallocate_list = new (mtClass) GrowableArray<Metadata*>(100, mtClass);
 871     }
 872     _deallocate_list->append_if_missing(m);
 873     ResourceMark rm;
 874     log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
 875     ClassLoaderDataGraph::set_should_clean_deallocate_lists();
 876   }
 877 }
 878 
 879 // Deallocate free metadata on the free list.  How useful the PermGen was!
 880 void ClassLoaderData::free_deallocate_list() {
 881   // This must be called at a safepoint because it depends on metadata walking at
 882   // safepoint cleanup time.
 883   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 884   assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
 885   if (_deallocate_list == nullptr) {
 886     return;
 887   }
 888   // Go backwards because this removes entries that are freed.
 889   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 890     Metadata* m = _deallocate_list->at(i);
 891     if (!m->on_stack()) {
 892       _deallocate_list->remove_at(i);
 893       // There are only three types of metadata that we deallocate directly.
 894       // Cast them so they can be used by the template function.
 895       if (m->is_method()) {
 896         MetadataFactory::free_metadata(this, (Method*)m);
 897       } else if (m->is_constantPool()) {
 898         MetadataFactory::free_metadata(this, (ConstantPool*)m);
 899       } else if (m->is_klass()) {
 900         if (!((Klass*)m)->is_inline_klass()) {
 901           MetadataFactory::free_metadata(this, (InstanceKlass*)m);
 902         } else {
 903           MetadataFactory::free_metadata(this, (InlineKlass*)m);
 904         }
 905       } else {
 906         ShouldNotReachHere();
 907       }
 908     } else {
 909       // Metadata is alive.
 910       // If scratch_class is on stack then it shouldn't be on this list!
 911       assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
 912              "scratch classes on this list should be dead");
 913       // Also should assert that other metadata on the list was found in handles.
 914       // Some cleaning remains.
 915       ClassLoaderDataGraph::set_should_clean_deallocate_lists();
 916     }
 917   }
 918 }
 919 
 920 // This is distinct from free_deallocate_list.  For class loader data that are
 921 // unloading, this frees the C heap memory for items on the list, and unlinks
 922 // scratch or error classes so that unloading events aren't triggered for these
 923 // classes. The metadata is removed with the unloading metaspace.
 924 // There isn't C heap memory allocated for methods, so nothing is done for them.
 925 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
 926   assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
 927   assert(is_unloading(), "only called for ClassLoaderData that are unloading");
 928   if (_deallocate_list == nullptr) {
 929     return;
 930   }
 931   // Go backwards because this removes entries that are freed.
 932   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 933     Metadata* m = _deallocate_list->at(i);
 934     _deallocate_list->remove_at(i);
 935     if (m->is_constantPool()) {
 936       ((ConstantPool*)m)->release_C_heap_structures();
 937     } else if (m->is_klass()) {
 938       InstanceKlass* ik = (InstanceKlass*)m;
 939       // also releases ik->constants() C heap memory
 940       ik->release_C_heap_structures();
 941       // Remove the class so unloading events aren't triggered for
 942       // this class (scratch or error class) in do_unloading().
 943       remove_class(ik);
 944       // But still have to remove it from the dumptime_table.
 945       SystemDictionaryShared::handle_class_unloading(ik);
 946     }
 947   }
 948 }
 949 
 950 // Caller needs ResourceMark
 951 // If the class loader's _name has not been explicitly set, the class loader's
 952 // qualified class name is returned.
 953 const char* ClassLoaderData::loader_name() const {
 954    if (_class_loader_klass == nullptr) {
 955      return BOOTSTRAP_LOADER_NAME;
 956    } else if (_name != nullptr) {
 957      return _name->as_C_string();
 958    } else {
 959      return _class_loader_klass->external_name();
 960    }
 961 }
 962 
 963 // Caller needs ResourceMark
 964 // Format of the _name_and_id is as follows:
 965 //   If the defining loader has a name explicitly set then '<loader-name>' @<id>
 966 //   If the defining loader has no name then <qualified-class-name> @<id>
 967 //   If built-in loader, then omit '@<id>' as there is only one instance.
 968 const char* ClassLoaderData::loader_name_and_id() const {
 969   if (_class_loader_klass == nullptr) {
 970     return "'" BOOTSTRAP_LOADER_NAME "'";
 971   } else if (_name_and_id != nullptr) {
 972     return _name_and_id->as_C_string();
 973   } else {
 974     // May be called in a race before _name_and_id is initialized.
 975     return _class_loader_klass->external_name();
 976   }
 977 }
 978 
 979 void ClassLoaderData::print_value_on(outputStream* out) const {
 980   if (!is_unloading() && class_loader() != nullptr) {
 981     out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
 982     class_loader()->print_value_on(out);  // includes loader_name_and_id() and address of class loader instance
 983   } else {
 984     // loader data: 0xsomeaddr of 'bootstrap'
 985     out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
 986   }
 987   if (_has_class_mirror_holder) {
 988     out->print(" has a class holder");
 989   }
 990 }
 991 
 992 void ClassLoaderData::print_value() const { print_value_on(tty); }
 993 
 994 #ifndef PRODUCT
 995 class PrintKlassClosure: public KlassClosure {
 996   outputStream* _out;
 997 public:
 998   PrintKlassClosure(outputStream* out): _out(out) { }
 999 
1000   void do_klass(Klass* k) {
1001     ResourceMark rm;
1002     _out->print("%s,", k->external_name());
1003   }
1004 };
1005 
1006 void ClassLoaderData::print_on(outputStream* out) const {
1007   ResourceMark rm;
1008   out->print_cr("ClassLoaderData(" INTPTR_FORMAT ")", p2i(this));
1009   out->print_cr(" - name                %s", loader_name_and_id());
1010   if (!_holder.is_null()) {
1011     out->print   (" - holder              ");
1012     _holder.print_on(out);
1013     out->print_cr("");
1014   }
1015   if (!_unloading) {
1016     out->print_cr(" - class loader        " INTPTR_FORMAT, p2i(_class_loader.peek()));
1017   } else {
1018     out->print_cr(" - class loader        <unloading, oop is bad>");
1019   }
1020   out->print_cr(" - metaspace           " INTPTR_FORMAT, p2i(_metaspace));
1021   out->print_cr(" - unloading           %s", _unloading ? "true" : "false");
1022   out->print_cr(" - class mirror holder %s", _has_class_mirror_holder ? "true" : "false");
1023   out->print_cr(" - modified oops       %s", _modified_oops ? "true" : "false");
1024   out->print_cr(" - _keep_alive_ref_count %d", _keep_alive_ref_count);
1025   out->print   (" - claim               ");
1026   switch(_claim) {
1027     case _claim_none:                       out->print_cr("none"); break;
1028     case _claim_finalizable:                out->print_cr("finalizable"); break;
1029     case _claim_strong:                     out->print_cr("strong"); break;
1030     case _claim_stw_fullgc_mark:            out->print_cr("stw full gc mark"); break;
1031     case _claim_stw_fullgc_adjust:          out->print_cr("stw full gc adjust"); break;
1032     case _claim_other:                      out->print_cr("other"); break;
1033     case _claim_other | _claim_finalizable: out->print_cr("other and finalizable"); break;
1034     case _claim_other | _claim_strong:      out->print_cr("other and strong"); break;
1035     default:                                ShouldNotReachHere();
1036   }
1037   out->print_cr(" - handles             %d", _handles.count());
1038   out->print_cr(" - dependency count    %d", _dependency_count);
1039   out->print   (" - klasses             { ");
1040   if (Verbose) {
1041     PrintKlassClosure closure(out);
1042     ((ClassLoaderData*)this)->classes_do(&closure);
1043   } else {
1044      out->print("...");
1045   }
1046   out->print_cr(" }");
1047   out->print_cr(" - packages            " INTPTR_FORMAT, p2i(_packages));
1048   out->print_cr(" - module              " INTPTR_FORMAT, p2i(_modules));
1049   out->print_cr(" - unnamed module      " INTPTR_FORMAT, p2i(_unnamed_module));
1050   if (_dictionary != nullptr) {
1051     out->print   (" - dictionary          " INTPTR_FORMAT " ", p2i(_dictionary));
1052     _dictionary->print_size(out);
1053   } else {
1054     out->print_cr(" - dictionary          " INTPTR_FORMAT, p2i(_dictionary));
1055   }
1056   if (_jmethod_ids != nullptr) {
1057     out->print   (" - jmethod count       ");
1058     Method::print_jmethod_ids_count(this, out);
1059     out->print_cr("");
1060   }
1061   out->print_cr(" - deallocate list     " INTPTR_FORMAT, p2i(_deallocate_list));
1062   out->print_cr(" - next CLD            " INTPTR_FORMAT, p2i(_next));
1063 }
1064 #endif // PRODUCT
1065 
1066 void ClassLoaderData::print() const { print_on(tty); }
1067 
1068 class VerifyHandleOops : public OopClosure {
1069   VerifyOopClosure vc;
1070  public:
1071   virtual void do_oop(oop* p) {
1072     if (p != nullptr && *p != nullptr) {
1073       oop o = *p;
1074       if (!java_lang_Class::is_instance(o)) {
1075         // is_instance will assert for an invalid oop.
1076         // Walk the resolved_references array and other assorted oops in the
1077         // CLD::_handles field.  The mirror oops are followed by other heap roots.
1078         o->oop_iterate(&vc);
1079       }
1080     }
1081   }
1082   virtual void do_oop(narrowOop* o) { ShouldNotReachHere(); }
1083 };
1084 
1085 void ClassLoaderData::verify() {
1086   assert_locked_or_safepoint(_metaspace_lock);
1087   oop cl = class_loader();
1088 
1089   guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same");
1090   guarantee(cl != nullptr || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be");
1091 
1092   // Verify the integrity of the allocated space.
1093 #ifdef ASSERT
1094   if (metaspace_or_null() != nullptr) {
1095     metaspace_or_null()->verify();
1096   }
1097 #endif
1098 
1099   for (Klass* k = _klasses; k != nullptr; k = k->next_link()) {
1100     guarantee(k->class_loader_data() == this, "Must be the same");
1101     k->verify();
1102     assert(k != k->next_link(), "no loops!");
1103   }
1104 
1105   if (_modules != nullptr) {
1106     _modules->verify();
1107   }
1108 
1109   if (_deallocate_list != nullptr) {
1110     for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
1111       Metadata* m = _deallocate_list->at(i);
1112       if (m->is_klass()) {
1113         ((Klass*)m)->verify();
1114       }
1115     }
1116   }
1117 
1118   // Check the oops in the handles area
1119   VerifyHandleOops vho;
1120   oops_do(&vho, _claim_none, false);
1121 }
1122 
1123 bool ClassLoaderData::contains_klass(Klass* klass) {
1124   // Lock-free access requires load_acquire
1125   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
1126     if (k == klass) return true;
1127   }
1128   return false;
1129 }