1 /*
   2  * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // A ClassLoaderData identifies the full set of class types that a class
  26 // loader's name resolution strategy produces for a given configuration of the
  27 // class loader.
  28 // Class types in the ClassLoaderData may be defined by from class file binaries
  29 // provided by the class loader, or from other class loader it interacts with
  30 // according to its name resolution strategy.
  31 //
  32 // Class loaders that implement a deterministic name resolution strategy
  33 // (including with respect to their delegation behavior), such as the boot, the
  34 // extension, 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/systemDictionary.hpp"
  55 #include "code/codeCache.hpp"
  56 #include "memory/gcLocker.hpp"
  57 #include "memory/metadataFactory.hpp"
  58 #include "memory/metaspaceShared.hpp"
  59 #include "memory/oopFactory.hpp"
  60 #include "runtime/jniHandles.hpp"
  61 #include "runtime/mutex.hpp"
  62 #include "runtime/safepoint.hpp"
  63 #include "runtime/synchronizer.hpp"
  64 #include "utilities/growableArray.hpp"
  65 #include "utilities/macros.hpp"
  66 #include "utilities/ostream.hpp"
  67 
  68 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
  69 
  70 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies) :
  71   _class_loader(h_class_loader()),
  72   _is_anonymous(is_anonymous),
  73   // An anonymous class loader data doesn't have anything to keep
  74   // it from being unloaded during parsing of the anonymous class.
  75   // The null-class-loader should always be kept alive.
  76   _keep_alive(is_anonymous || h_class_loader.is_null()),
  77   _metaspace(NULL), _unloading(false), _klasses(NULL),
  78   _claimed(0), _jmethod_ids(NULL), _handles(), _deallocate_list(NULL),
  79   _next(NULL), _dependencies(dependencies),
  80   _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true)) {
  81 
  82   JFR_ONLY(INIT_ID(this);)
  83 }
  84 
  85 void ClassLoaderData::init_dependencies(TRAPS) {
  86   assert(!Universe::is_fully_initialized(), "should only be called when initializing");
  87   assert(is_the_null_class_loader_data(), "should only call this for the null class loader");
  88   _dependencies.init(CHECK);
  89 }
  90 
  91 void ClassLoaderData::Dependencies::init(TRAPS) {
  92   // Create empty dependencies array to add to. CMS requires this to be
  93   // an oop so that it can track additions via card marks.  We think.
  94   _list_head = oopFactory::new_objectArray(2, CHECK);
  95 }
  96 
  97 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
  98   Chunk* c = _head;
  99   while (c != NULL) {
 100     Chunk* next = c->_next;
 101     delete c;
 102     c = next;
 103   }
 104 }
 105 
 106 oop* ClassLoaderData::ChunkedHandleList::add(oop o) {
 107   if (_head == NULL || _head->_size == Chunk::CAPACITY) {
 108     Chunk* next = new Chunk(_head);
 109     OrderAccess::release_store_ptr(&_head, next);
 110   }
 111   oop* handle = &_head->_data[_head->_size];
 112   *handle = o;
 113   OrderAccess::release_store(&_head->_size, _head->_size + 1);
 114   return handle;
 115 }
 116 
 117 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
 118   for (juint i = 0; i < size; i++) {
 119     if (c->_data[i] != NULL) {
 120       f->do_oop(&c->_data[i]);
 121     }
 122   }
 123 }
 124 
 125 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
 126   Chunk* head = (Chunk*) OrderAccess::load_ptr_acquire(&_head);
 127   if (head != NULL) {
 128     // Must be careful when reading size of head
 129     oops_do_chunk(f, head, OrderAccess::load_acquire(&head->_size));
 130     for (Chunk* c = head->_next; c != NULL; c = c->_next) {
 131       oops_do_chunk(f, c, c->_size);
 132     }
 133   }
 134 }
 135 
 136 bool ClassLoaderData::claim() {
 137   if (_claimed == 1) {
 138     return false;
 139   }
 140 
 141   return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;
 142 }
 143 
 144 void ClassLoaderData::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 145   if (must_claim && !claim()) {
 146     return;
 147   }
 148 
 149   f->do_oop(&_class_loader);
 150   _dependencies.oops_do(f);
 151   _handles.oops_do(f);
 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   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 163     klass_closure->do_klass(k);
 164     assert(k != k->next_link(), "no loops!");
 165   }
 166 }
 167 
 168 void ClassLoaderData::classes_do(void f(Klass * const)) {
 169   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 170     f(k);
 171   }
 172 }
 173 
 174 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
 175   // Lock to avoid classes being modified/added/removed during iteration
 176   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 177   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 178     // Do not filter ArrayKlass oops here...
 179     if (k->oop_is_array() || (k->oop_is_instance() && InstanceKlass::cast(k)->is_loaded())) {
 180       klass_closure->do_klass(k);
 181     }
 182   }
 183 }
 184 
 185 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
 186   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 187     if (k->oop_is_instance()) {
 188       f(InstanceKlass::cast(k));
 189     }
 190     assert(k != k->next_link(), "no loops!");
 191   }
 192 }
 193 
 194 void ClassLoaderData::record_dependency(Klass* k, TRAPS) {
 195   ClassLoaderData * const from_cld = this;
 196   ClassLoaderData * const to_cld = k->class_loader_data();
 197 
 198   // Dependency to the null class loader data doesn't need to be recorded
 199   // because the null class loader data never goes away.
 200   if (to_cld->is_the_null_class_loader_data()) {
 201     return;
 202   }
 203 
 204   oop to;
 205   if (to_cld->is_anonymous()) {
 206     // Anonymous class dependencies are through the mirror.
 207     to = k->java_mirror();
 208   } else {
 209     to = to_cld->class_loader();
 210 
 211     // If from_cld is anonymous, even if it's class_loader is a parent of 'to'
 212     // we still have to add it.  The class_loader won't keep from_cld alive.
 213     if (!from_cld->is_anonymous()) {
 214       // Check that this dependency isn't from the same or parent class_loader
 215       oop from = from_cld->class_loader();
 216 
 217       oop curr = from;
 218       while (curr != NULL) {
 219         if (curr == to) {
 220           return; // this class loader is in the parent list, no need to add it.
 221         }
 222         curr = java_lang_ClassLoader::parent(curr);
 223       }
 224     }
 225   }
 226 
 227   // It's a dependency we won't find through GC, add it. This is relatively rare
 228   // Must handle over GC point.
 229   Handle dependency(THREAD, to);
 230   from_cld->_dependencies.add(dependency, CHECK);
 231 }
 232 
 233 
 234 void ClassLoaderData::Dependencies::add(Handle dependency, TRAPS) {
 235   // Check first if this dependency is already in the list.
 236   // Save a pointer to the last to add to under the lock.
 237   objArrayOop ok = _list_head;
 238   objArrayOop last = NULL;
 239   while (ok != NULL) {
 240     last = ok;
 241     if (ok->obj_at(0) == dependency()) {
 242       // Don't need to add it
 243       return;
 244     }
 245     ok = (objArrayOop)ok->obj_at(1);
 246   }
 247 
 248   // Must handle over GC points
 249   assert (last != NULL, "dependencies should be initialized");
 250   objArrayHandle last_handle(THREAD, last);
 251 
 252   // Create a new dependency node with fields for (class_loader or mirror, next)
 253   objArrayOop deps = oopFactory::new_objectArray(2, CHECK);
 254   deps->obj_at_put(0, dependency());
 255 
 256   // Must handle over GC points
 257   objArrayHandle new_dependency(THREAD, deps);
 258 
 259   // Add the dependency under lock
 260   locked_add(last_handle, new_dependency, THREAD);
 261 }
 262 
 263 void ClassLoaderData::Dependencies::locked_add(objArrayHandle last_handle,
 264                                                objArrayHandle new_dependency,
 265                                                Thread* THREAD) {
 266 
 267   // Have to lock and put the new dependency on the end of the dependency
 268   // array so the card mark for CMS sees that this dependency is new.
 269   // Can probably do this lock free with some effort.
 270   ObjectLocker ol(Handle(THREAD, _list_head), THREAD);
 271 
 272   oop loader_or_mirror = new_dependency->obj_at(0);
 273 
 274   // Since the dependencies are only added, add to the end.
 275   objArrayOop end = last_handle();
 276   objArrayOop last = NULL;
 277   while (end != NULL) {
 278     last = end;
 279     // check again if another thread added it to the end.
 280     if (end->obj_at(0) == loader_or_mirror) {
 281       // Don't need to add it
 282       return;
 283     }
 284     end = (objArrayOop)end->obj_at(1);
 285   }
 286   assert (last != NULL, "dependencies should be initialized");
 287   // fill in the first element with the oop in new_dependency.
 288   if (last->obj_at(0) == NULL) {
 289     last->obj_at_put(0, new_dependency->obj_at(0));
 290   } else {
 291     last->obj_at_put(1, new_dependency());
 292   }
 293 }
 294 
 295 void ClassLoaderDataGraph::clear_claimed_marks() {
 296   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 297     cld->clear_claimed();
 298   }
 299 }
 300 
 301 void ClassLoaderData::add_class(Klass* k) {
 302   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 303   Klass* old_value = _klasses;
 304   k->set_next_link(old_value);
 305   // link the new item into the list
 306   _klasses = k;
 307 
 308   if (TraceClassLoaderData && Verbose && k->class_loader_data() != NULL) {
 309     ResourceMark rm;
 310     tty->print_cr("[TraceClassLoaderData] Adding k: " PTR_FORMAT " %s to CLD: "
 311                   PTR_FORMAT " loader: " PTR_FORMAT " %s",
 312                   p2i(k),
 313                   k->external_name(),
 314                   p2i(k->class_loader_data()),
 315                   p2i((void *)k->class_loader()),
 316                   loader_name());
 317   }
 318 }
 319 
 320 // This is called by InstanceKlass::deallocate_contents() to remove the
 321 // scratch_class for redefine classes.  We need a lock because there it may not
 322 // be called at a safepoint if there's an error.
 323 void ClassLoaderData::remove_class(Klass* scratch_class) {
 324   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 325   Klass* prev = NULL;
 326   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 327     if (k == scratch_class) {
 328       if (prev == NULL) {
 329         _klasses = k->next_link();
 330       } else {
 331         Klass* next = k->next_link();
 332         prev->set_next_link(next);
 333       }
 334       return;
 335     }
 336     prev = k;
 337     assert(k != k->next_link(), "no loops!");
 338   }
 339   ShouldNotReachHere();   // should have found this class!!
 340 }
 341 
 342 void ClassLoaderData::unload() {
 343   _unloading = true;
 344 
 345   // Tell serviceability tools these classes are unloading
 346   classes_do(InstanceKlass::notify_unload_class);
 347 
 348   if (TraceClassLoaderData) {
 349     ResourceMark rm;
 350     tty->print("[ClassLoaderData: unload loader data " INTPTR_FORMAT, p2i(this));
 351     tty->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)class_loader()),
 352                loader_name());
 353     if (is_anonymous()) {
 354       tty->print(" for anonymous class  " INTPTR_FORMAT " ", p2i(_klasses));
 355     }
 356     tty->print_cr("]");
 357   }
 358 }
 359 
 360 oop ClassLoaderData::keep_alive_object() const {
 361   assert(!keep_alive(), "Don't use with CLDs that are artificially kept alive");
 362   return is_anonymous() ? _klasses->java_mirror() : class_loader();
 363 }
 364 
 365 bool ClassLoaderData::is_alive(BoolObjectClosure* is_alive_closure) const {
 366   bool alive = keep_alive() // null class loader and incomplete anonymous klasses.
 367       || is_alive_closure->do_object_b(keep_alive_object());
 368 
 369   return alive;
 370 }
 371 
 372 
 373 ClassLoaderData::~ClassLoaderData() {
 374   // Release C heap structures for all the classes.
 375   classes_do(InstanceKlass::release_C_heap_structures);
 376 
 377   Metaspace *m = _metaspace;
 378   if (m != NULL) {
 379     _metaspace = NULL;
 380     // release the metaspace
 381     delete m;
 382   }
 383 
 384   // Clear all the JNI handles for methods
 385   // These aren't deallocated and are going to look like a leak, but that's
 386   // needed because we can't really get rid of jmethodIDs because we don't
 387   // know when native code is going to stop using them.  The spec says that
 388   // they're "invalid" but existing programs likely rely on their being
 389   // NULL after class unloading.
 390   if (_jmethod_ids != NULL) {
 391     Method::clear_jmethod_ids(this);
 392   }
 393   // Delete lock
 394   delete _metaspace_lock;
 395 
 396   // Delete free list
 397   if (_deallocate_list != NULL) {
 398     delete _deallocate_list;
 399   }
 400 }
 401 
 402 /**
 403  * Returns true if this class loader data is for the extension class loader.
 404  */
 405 bool ClassLoaderData::is_ext_class_loader_data() const {
 406   return SystemDictionary::is_ext_class_loader(class_loader());
 407 }
 408 
 409 Metaspace* ClassLoaderData::metaspace_non_null() {
 410   assert(!DumpSharedSpaces, "wrong metaspace!");
 411   // If the metaspace has not been allocated, create a new one.  Might want
 412   // to create smaller arena for Reflection class loaders also.
 413   // The reason for the delayed allocation is because some class loaders are
 414   // simply for delegating with no metadata of their own.
 415   if (_metaspace == NULL) {
 416     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 417     // Check again if metaspace has been allocated while we were getting this lock.
 418     if (_metaspace != NULL) {
 419       return _metaspace;
 420     }
 421     if (this == the_null_class_loader_data()) {
 422       assert (class_loader() == NULL, "Must be");
 423       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType));
 424     } else if (is_anonymous()) {
 425       if (TraceClassLoaderData && Verbose && class_loader() != NULL) {
 426         tty->print_cr("is_anonymous: %s", class_loader()->klass()->internal_name());
 427       }
 428       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType));
 429     } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
 430       if (TraceClassLoaderData && Verbose && class_loader() != NULL) {
 431         tty->print_cr("is_reflection: %s", class_loader()->klass()->internal_name());
 432       }
 433       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType));
 434     } else {
 435       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType));
 436     }
 437   }
 438   return _metaspace;
 439 }
 440 
 441 jobject ClassLoaderData::add_handle(Handle h) {
 442   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 443   return (jobject) _handles.add(h());
 444 }
 445 
 446 // Add this metadata pointer to be freed when it's safe.  This is only during
 447 // class unloading because Handles might point to this metadata field.
 448 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
 449   // Metadata in shared region isn't deleted.
 450   if (!m->is_shared()) {
 451     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 452     if (_deallocate_list == NULL) {
 453       _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, true);
 454     }
 455     _deallocate_list->append_if_missing(m);
 456   }
 457 }
 458 
 459 // Deallocate free metadata on the free list.  How useful the PermGen was!
 460 void ClassLoaderData::free_deallocate_list() {
 461   // Don't need lock, at safepoint
 462   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 463   if (_deallocate_list == NULL) {
 464     return;
 465   }
 466   // Go backwards because this removes entries that are freed.
 467   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 468     Metadata* m = _deallocate_list->at(i);
 469     if (!m->on_stack()) {
 470       _deallocate_list->remove_at(i);
 471       // There are only three types of metadata that we deallocate directly.
 472       // Cast them so they can be used by the template function.
 473       if (m->is_method()) {
 474         MetadataFactory::free_metadata(this, (Method*)m);
 475       } else if (m->is_constantPool()) {
 476         MetadataFactory::free_metadata(this, (ConstantPool*)m);
 477       } else if (m->is_klass()) {
 478         MetadataFactory::free_metadata(this, (InstanceKlass*)m);
 479       } else {
 480         ShouldNotReachHere();
 481       }
 482     }
 483   }
 484 }
 485 
 486 // These anonymous class loaders are to contain classes used for JSR292
 487 ClassLoaderData* ClassLoaderData::anonymous_class_loader_data(oop loader, TRAPS) {
 488   // Add a new class loader data to the graph.
 489   return ClassLoaderDataGraph::add(loader, true, THREAD);
 490 }
 491 
 492 const char* ClassLoaderData::loader_name() {
 493   // Handles null class loader
 494   return SystemDictionary::loader_name(class_loader());
 495 }
 496 
 497 #ifndef PRODUCT
 498 // Define to dump klasses
 499 #undef CLD_DUMP_KLASSES
 500 
 501 void ClassLoaderData::dump(outputStream * const out) {
 502   ResourceMark rm;
 503   out->print("ClassLoaderData CLD: " PTR_FORMAT ", loader: " PTR_FORMAT ", loader_klass: " PTR_FORMAT " %s {",
 504       p2i(this), p2i((void *)class_loader()),
 505       p2i(class_loader() != NULL ? class_loader()->klass() : NULL), loader_name());
 506   if (claimed()) out->print(" claimed ");
 507   if (is_unloading()) out->print(" unloading ");
 508   out->cr();
 509   if (metaspace_or_null() != NULL) {
 510     out->print_cr("metaspace: " INTPTR_FORMAT, p2i(metaspace_or_null()));
 511     metaspace_or_null()->dump(out);
 512   } else {
 513     out->print_cr("metaspace: NULL");
 514   }
 515 
 516 #ifdef CLD_DUMP_KLASSES
 517   if (Verbose) {
 518     ResourceMark rm;
 519     Klass* k = _klasses;
 520     while (k != NULL) {
 521       out->print_cr("klass " PTR_FORMAT ", %s, CT: %d, MUT: %d", k, k->name()->as_C_string(),
 522           k->has_modified_oops(), k->has_accumulated_modified_oops());
 523       assert(k != k->next_link(), "no loops!");
 524       k = k->next_link();
 525     }
 526   }
 527 #endif  // CLD_DUMP_KLASSES
 528 #undef CLD_DUMP_KLASSES
 529   if (_jmethod_ids != NULL) {
 530     Method::print_jmethod_ids(this, out);
 531   }
 532   out->print_cr("}");
 533 }
 534 #endif // PRODUCT
 535 
 536 void ClassLoaderData::verify() {
 537   oop cl = class_loader();
 538 
 539   guarantee(this == class_loader_data(cl) || is_anonymous(), "Must be the same");
 540   guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || is_anonymous(), "must be");
 541 
 542   // Verify the integrity of the allocated space.
 543   if (metaspace_or_null() != NULL) {
 544     metaspace_or_null()->verify();
 545   }
 546 
 547   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 548     guarantee(k->class_loader_data() == this, "Must be the same");
 549     k->verify();
 550     assert(k != k->next_link(), "no loops!");
 551   }
 552 }
 553 
 554 bool ClassLoaderData::contains_klass(Klass* klass) {
 555   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 556     if (k == klass) return true;
 557   }
 558   return false;
 559 }
 560 
 561 
 562 // GC root of class loader data created.
 563 ClassLoaderData* ClassLoaderDataGraph::_head = NULL;
 564 ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
 565 ClassLoaderData* ClassLoaderDataGraph::_saved_unloading = NULL;
 566 ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
 567 
 568 bool ClassLoaderDataGraph::_should_purge = false;
 569 
 570 // Add a new class loader data node to the list.  Assign the newly created
 571 // ClassLoaderData into the java/lang/ClassLoader object as a hidden field
 572 ClassLoaderData* ClassLoaderDataGraph::add(Handle loader, bool is_anonymous, TRAPS) {
 573   // We need to allocate all the oops for the ClassLoaderData before allocating the
 574   // actual ClassLoaderData object.
 575   ClassLoaderData::Dependencies dependencies(CHECK_NULL);
 576 
 577   No_Safepoint_Verifier no_safepoints; // we mustn't GC until we've installed the
 578                                        // ClassLoaderData in the graph since the CLD
 579                                        // contains unhandled oops
 580 
 581   ClassLoaderData* cld = new ClassLoaderData(loader, is_anonymous, dependencies);
 582 
 583 
 584   if (!is_anonymous) {
 585     ClassLoaderData** cld_addr = java_lang_ClassLoader::loader_data_addr(loader());
 586     // First, Atomically set it
 587     ClassLoaderData* old = (ClassLoaderData*) Atomic::cmpxchg_ptr(cld, cld_addr, NULL);
 588     if (old != NULL) {
 589       delete cld;
 590       // Returns the data.
 591       return old;
 592     }
 593   }
 594 
 595   // We won the race, and therefore the task of adding the data to the list of
 596   // class loader data
 597   ClassLoaderData** list_head = &_head;
 598   ClassLoaderData* next = _head;
 599 
 600   do {
 601     cld->set_next(next);
 602     ClassLoaderData* exchanged = (ClassLoaderData*)Atomic::cmpxchg_ptr(cld, list_head, next);
 603     if (exchanged == next) {
 604       if (TraceClassLoaderData) {
 605         ResourceMark rm;
 606         tty->print("[ClassLoaderData: ");
 607         tty->print("create class loader data " INTPTR_FORMAT, p2i(cld));
 608         tty->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)cld->class_loader()),
 609                    cld->loader_name());
 610         tty->print_cr("]");
 611       }
 612       return cld;
 613     }
 614     next = exchanged;
 615   } while (true);
 616 
 617 }
 618 
 619 void ClassLoaderDataGraph::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 620   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 621     cld->oops_do(f, klass_closure, must_claim);
 622   }
 623 }
 624 
 625 void ClassLoaderDataGraph::keep_alive_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 626   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 627     if (cld->keep_alive()) {
 628       cld->oops_do(f, klass_closure, must_claim);
 629     }
 630   }
 631 }
 632 
 633 void ClassLoaderDataGraph::always_strong_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 634   if (ClassUnloading) {
 635     keep_alive_oops_do(f, klass_closure, must_claim);
 636   } else {
 637     oops_do(f, klass_closure, must_claim);
 638   }
 639 }
 640 
 641 void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {
 642   for (ClassLoaderData* cld = _head; cl != NULL && cld != NULL; cld = cld->next()) {
 643     cl->do_cld(cld);
 644   }
 645 }
 646 
 647 void ClassLoaderDataGraph::cld_unloading_do(CLDClosure* cl) {
 648   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 649   // Only walk the head until any clds not purged from prior unloading
 650   // (CMS doesn't purge right away).
 651   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 652     assert(cld->is_unloading(), "invariant");
 653     cl->do_cld(cld);
 654   }
 655 }
 656 
 657 void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {
 658   for (ClassLoaderData* cld = _head;  cld != NULL; cld = cld->_next) {
 659     CLDClosure* closure = cld->keep_alive() ? strong : weak;
 660     if (closure != NULL) {
 661       closure->do_cld(cld);
 662     }
 663   }
 664 }
 665 
 666 void ClassLoaderDataGraph::keep_alive_cld_do(CLDClosure* cl) {
 667   roots_cld_do(cl, NULL);
 668 }
 669 
 670 void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
 671   if (ClassUnloading) {
 672     keep_alive_cld_do(cl);
 673   } else {
 674     cld_do(cl);
 675   }
 676 }
 677 
 678 void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
 679   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 680     cld->classes_do(klass_closure);
 681   }
 682 }
 683 
 684 void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
 685   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 686     cld->classes_do(f);
 687   }
 688 }
 689 
 690 void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
 691   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 692     cld->loaded_classes_do(klass_closure);
 693   }
 694 }
 695 
 696 void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
 697   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 698   // Only walk the head until any clds not purged from prior unloading
 699   // (CMS doesn't purge right away).
 700   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 701     cld->classes_do(f);
 702   }
 703 }
 704 
 705 GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
 706   assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
 707 
 708   GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
 709 
 710   // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
 711   ClassLoaderData* curr = _head;
 712   while (curr != _saved_head) {
 713     if (!curr->claimed()) {
 714       array->push(curr);
 715 
 716       if (TraceClassLoaderData) {
 717         tty->print("[ClassLoaderData] found new CLD: ");
 718         curr->print_value_on(tty);
 719         tty->cr();
 720       }
 721     }
 722 
 723     curr = curr->_next;
 724   }
 725 
 726   return array;
 727 }
 728 
 729 bool ClassLoaderDataGraph::unload_list_contains(const void* x) {
 730   assert(SafepointSynchronize::is_at_safepoint(), "only safe to call at safepoint");
 731   for (ClassLoaderData* cld = _unloading; cld != NULL; cld = cld->next()) {
 732     if (cld->metaspace_or_null() != NULL && cld->metaspace_or_null()->contains(x)) {
 733       return true;
 734     }
 735   }
 736   return false;
 737 }
 738 
 739 #ifndef PRODUCT
 740 bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
 741   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 742     if (loader_data == data) {
 743       return true;
 744     }
 745   }
 746 
 747   return false;
 748 }
 749 #endif // PRODUCT
 750 
 751 // Move class loader data from main list to the unloaded list for unloading
 752 // and deallocation later.
 753 bool ClassLoaderDataGraph::do_unloading(BoolObjectClosure* is_alive_closure, bool clean_alive) {
 754   ClassLoaderData* data = _head;
 755   ClassLoaderData* prev = NULL;
 756   bool seen_dead_loader = false;
 757 
 758   // Save previous _unloading pointer for CMS which may add to unloading list before
 759   // purging and we don't want to rewalk the previously unloaded class loader data.
 760   _saved_unloading = _unloading;
 761 
 762   while (data != NULL) {
 763     if (data->is_alive(is_alive_closure)) {
 764       prev = data;
 765       data = data->next();
 766       continue;
 767     }
 768     seen_dead_loader = true;
 769     ClassLoaderData* dead = data;
 770     dead->unload();
 771     data = data->next();
 772     // Remove from loader list.
 773     // This class loader data will no longer be found
 774     // in the ClassLoaderDataGraph.
 775     if (prev != NULL) {
 776       prev->set_next(data);
 777     } else {
 778       assert(dead == _head, "sanity check");
 779       _head = data;
 780     }
 781     dead->set_next(_unloading);
 782     _unloading = dead;
 783   }
 784 
 785   if (clean_alive) {
 786     // Clean previous versions and the deallocate list.
 787     ClassLoaderDataGraph::clean_metaspaces();
 788   }
 789 
 790   return seen_dead_loader;
 791 }
 792 
 793 void ClassLoaderDataGraph::clean_metaspaces() {
 794   // mark metadata seen on the stack and code cache so we can delete unneeded entries.
 795   bool has_redefined_a_class = JvmtiExport::has_redefined_a_class();
 796   MetadataOnStackMark md_on_stack(has_redefined_a_class);
 797 
 798   if (has_redefined_a_class) {
 799     // purge_previous_versions also cleans weak method links. Because
 800     // one method's MDO can reference another method from another
 801     // class loader, we need to first clean weak method links for all
 802     // class loaders here. Below, we can then free redefined methods
 803     // for all class loaders.
 804     for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 805       data->classes_do(InstanceKlass::purge_previous_versions);
 806     }
 807   }
 808 
 809   // Need to purge the previous version before deallocating.
 810   free_deallocate_lists();
 811 }
 812 
 813 void ClassLoaderDataGraph::purge() {
 814   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 815   ClassLoaderData* list = _unloading;
 816   _unloading = NULL;
 817   ClassLoaderData* next = list;
 818   while (next != NULL) {
 819     ClassLoaderData* purge_me = next;
 820     next = purge_me->next();
 821     delete purge_me;
 822   }
 823   Metaspace::purge();
 824 }
 825 
 826 void ClassLoaderDataGraph::free_deallocate_lists() {
 827   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 828     // We need to keep this data until InstanceKlass::purge_previous_version has been
 829     // called on all alive classes. See the comment in ClassLoaderDataGraph::clean_metaspaces.
 830     cld->free_deallocate_list();
 831   }
 832 
 833   // In some rare cases items added to the unloading list will not be freed elsewhere.
 834   // To keep it simple, walk the _unloading list also.
 835   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 836     cld->free_deallocate_list();
 837   }
 838 }
 839 
 840 // CDS support
 841 
 842 // Global metaspaces for writing information to the shared archive.  When
 843 // application CDS is supported, we may need one per metaspace, so this
 844 // sort of looks like it.
 845 Metaspace* ClassLoaderData::_ro_metaspace = NULL;
 846 Metaspace* ClassLoaderData::_rw_metaspace = NULL;
 847 static bool _shared_metaspaces_initialized = false;
 848 
 849 // Initialize shared metaspaces (change to call from somewhere not lazily)
 850 void ClassLoaderData::initialize_shared_metaspaces() {
 851   assert(DumpSharedSpaces, "only use this for dumping shared spaces");
 852   assert(this == ClassLoaderData::the_null_class_loader_data(),
 853          "only supported for null loader data for now");
 854   assert (!_shared_metaspaces_initialized, "only initialize once");
 855   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 856   _ro_metaspace = new Metaspace(_metaspace_lock, Metaspace::ROMetaspaceType);
 857   _rw_metaspace = new Metaspace(_metaspace_lock, Metaspace::ReadWriteMetaspaceType);
 858   _shared_metaspaces_initialized = true;
 859 }
 860 
 861 Metaspace* ClassLoaderData::ro_metaspace() {
 862   assert(_ro_metaspace != NULL, "should already be initialized");
 863   return _ro_metaspace;
 864 }
 865 
 866 Metaspace* ClassLoaderData::rw_metaspace() {
 867   assert(_rw_metaspace != NULL, "should already be initialized");
 868   return _rw_metaspace;
 869 }
 870 
 871 ClassLoaderDataGraphKlassIteratorAtomic::ClassLoaderDataGraphKlassIteratorAtomic()
 872     : _next_klass(NULL) {
 873   ClassLoaderData* cld = ClassLoaderDataGraph::_head;
 874   Klass* klass = NULL;
 875 
 876   // Find the first klass in the CLDG.
 877   while (cld != NULL) {
 878     klass = cld->_klasses;
 879     if (klass != NULL) {
 880       _next_klass = klass;
 881       return;
 882     }
 883     cld = cld->next();
 884   }
 885 }
 886 
 887 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass_in_cldg(Klass* klass) {
 888   Klass* next = klass->next_link();
 889   if (next != NULL) {
 890     return next;
 891   }
 892 
 893   // No more klasses in the current CLD. Time to find a new CLD.
 894   ClassLoaderData* cld = klass->class_loader_data();
 895   while (next == NULL) {
 896     cld = cld->next();
 897     if (cld == NULL) {
 898       break;
 899     }
 900     next = cld->_klasses;
 901   }
 902 
 903   return next;
 904 }
 905 
 906 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass() {
 907   Klass* head = _next_klass;
 908 
 909   while (head != NULL) {
 910     Klass* next = next_klass_in_cldg(head);
 911 
 912     Klass* old_head = (Klass*)Atomic::cmpxchg_ptr(next, &_next_klass, head);
 913 
 914     if (old_head == head) {
 915       return head; // Won the CAS.
 916     }
 917 
 918     head = old_head;
 919   }
 920 
 921   // Nothing more for the iterator to hand out.
 922   assert(head == NULL, err_msg("head is " PTR_FORMAT ", expected not null:", p2i(head)));
 923   return NULL;
 924 }
 925 
 926 ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
 927   _data = ClassLoaderDataGraph::_head;
 928 }
 929 
 930 ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
 931 
 932 #ifndef PRODUCT
 933 // callable from debugger
 934 extern "C" int print_loader_data_graph() {
 935   ClassLoaderDataGraph::dump_on(tty);
 936   return 0;
 937 }
 938 
 939 void ClassLoaderDataGraph::verify() {
 940   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 941     data->verify();
 942   }
 943 }
 944 
 945 void ClassLoaderDataGraph::dump_on(outputStream * const out) {
 946   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 947     data->dump(out);
 948   }
 949   MetaspaceAux::dump(out);
 950 }
 951 #endif // PRODUCT
 952 
 953 void ClassLoaderData::print_value_on(outputStream* out) const {
 954   if (class_loader() == NULL) {
 955     out->print("NULL class_loader");
 956   } else {
 957     out->print("class loader " INTPTR_FORMAT, p2i(this));
 958     class_loader()->print_value_on(out);
 959   }
 960 }