1 /*
   2  * Copyright (c) 2012, 2014, 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/atomic.inline.hpp"
  61 #include "runtime/jniHandles.hpp"
  62 #include "runtime/mutex.hpp"
  63 #include "runtime/safepoint.hpp"
  64 #include "runtime/synchronizer.hpp"
  65 #include "utilities/growableArray.hpp"
  66 #include "utilities/macros.hpp"
  67 #include "utilities/ostream.hpp"
  68 
  69 #if INCLUDE_TRACE
  70  #include "trace/tracing.hpp"
  71 #endif
  72 
  73 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
  74 
  75 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies) :
  76   _class_loader(h_class_loader()),
  77   _is_anonymous(is_anonymous),
  78   // An anonymous class loader data doesn't have anything to keep
  79   // it from being unloaded during parsing of the anonymous class.
  80   // The null-class-loader should always be kept alive.
  81   _keep_alive(is_anonymous || h_class_loader.is_null()),
  82   _metaspace(NULL), _unloading(false), _klasses(NULL),
  83   _claimed(0), _jmethod_ids(NULL), _handles(NULL), _deallocate_list(NULL),
  84   _next(NULL), _dependencies(dependencies),
  85   _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true)) {
  86     // empty
  87 }
  88 
  89 void ClassLoaderData::init_dependencies(TRAPS) {
  90   assert(!Universe::is_fully_initialized(), "should only be called when initializing");
  91   assert(is_the_null_class_loader_data(), "should only call this for the null class loader");
  92   _dependencies.init(CHECK);
  93 }
  94 
  95 void ClassLoaderData::Dependencies::init(TRAPS) {
  96   // Create empty dependencies array to add to. CMS requires this to be
  97   // an oop so that it can track additions via card marks.  We think.
  98   _list_head = oopFactory::new_objectArray(2, CHECK);
  99 }
 100 
 101 bool ClassLoaderData::claim() {
 102   if (_claimed == 1) {
 103     return false;
 104   }
 105 
 106   return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;
 107 }
 108 
 109 void ClassLoaderData::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 110   if (must_claim && !claim()) {
 111     return;
 112   }
 113 
 114   f->do_oop(&_class_loader);
 115   _dependencies.oops_do(f);
 116   _handles->oops_do(f);
 117   if (klass_closure != NULL) {
 118     classes_do(klass_closure);
 119   }
 120 }
 121 
 122 void ClassLoaderData::Dependencies::oops_do(OopClosure* f) {
 123   f->do_oop((oop*)&_list_head);
 124 }
 125 
 126 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
 127   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 128     klass_closure->do_klass(k);
 129     assert(k != k->next_link(), "no loops!");
 130   }
 131 }
 132 
 133 void ClassLoaderData::classes_do(void f(Klass * const)) {
 134   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 135     f(k);
 136   }
 137 }
 138 
 139 void ClassLoaderData::methods_do(void f(Method*)) {
 140   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 141     if (k->oop_is_instance()) {
 142       InstanceKlass::cast(k)->methods_do(f);
 143     }
 144   }
 145 }
 146 
 147 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
 148   // Lock to avoid classes being modified/added/removed during iteration
 149   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 150   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 151     // Do not filter ArrayKlass oops here...
 152     if (k->oop_is_array() || (k->oop_is_instance() && InstanceKlass::cast(k)->is_loaded())) {
 153       klass_closure->do_klass(k);
 154     }
 155   }
 156 }
 157 
 158 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
 159   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 160     if (k->oop_is_instance()) {
 161       f(InstanceKlass::cast(k));
 162     }
 163     assert(k != k->next_link(), "no loops!");
 164   }
 165 }
 166 
 167 void ClassLoaderData::record_dependency(Klass* k, TRAPS) {
 168   ClassLoaderData * const from_cld = this;
 169   ClassLoaderData * const to_cld = k->class_loader_data();
 170 
 171   // Dependency to the null class loader data doesn't need to be recorded
 172   // because the null class loader data never goes away.
 173   if (to_cld->is_the_null_class_loader_data()) {
 174     return;
 175   }
 176 
 177   oop to;
 178   if (to_cld->is_anonymous()) {
 179     // Anonymous class dependencies are through the mirror.
 180     to = k->java_mirror();
 181   } else {
 182     to = to_cld->class_loader();
 183 
 184     // If from_cld is anonymous, even if it's class_loader is a parent of 'to'
 185     // we still have to add it.  The class_loader won't keep from_cld alive.
 186     if (!from_cld->is_anonymous()) {
 187       // Check that this dependency isn't from the same or parent class_loader
 188       oop from = from_cld->class_loader();
 189 
 190       oop curr = from;
 191       while (curr != NULL) {
 192         if (curr == to) {
 193           return; // this class loader is in the parent list, no need to add it.
 194         }
 195         curr = java_lang_ClassLoader::parent(curr);
 196       }
 197     }
 198   }
 199 
 200   // It's a dependency we won't find through GC, add it. This is relatively rare
 201   // Must handle over GC point.
 202   Handle dependency(THREAD, to);
 203   from_cld->_dependencies.add(dependency, CHECK);
 204 }
 205 
 206 
 207 void ClassLoaderData::Dependencies::add(Handle dependency, TRAPS) {
 208   // Check first if this dependency is already in the list.
 209   // Save a pointer to the last to add to under the lock.
 210   objArrayOop ok = _list_head;
 211   objArrayOop last = NULL;
 212   while (ok != NULL) {
 213     last = ok;
 214     if (ok->obj_at(0) == dependency()) {
 215       // Don't need to add it
 216       return;
 217     }
 218     ok = (objArrayOop)ok->obj_at(1);
 219   }
 220 
 221   // Must handle over GC points
 222   assert (last != NULL, "dependencies should be initialized");
 223   objArrayHandle last_handle(THREAD, last);
 224 
 225   // Create a new dependency node with fields for (class_loader or mirror, next)
 226   objArrayOop deps = oopFactory::new_objectArray(2, CHECK);
 227   deps->obj_at_put(0, dependency());
 228 
 229   // Must handle over GC points
 230   objArrayHandle new_dependency(THREAD, deps);
 231 
 232   // Add the dependency under lock
 233   locked_add(last_handle, new_dependency, THREAD);
 234 }
 235 
 236 void ClassLoaderData::Dependencies::locked_add(objArrayHandle last_handle,
 237                                                objArrayHandle new_dependency,
 238                                                Thread* THREAD) {
 239 
 240   // Have to lock and put the new dependency on the end of the dependency
 241   // array so the card mark for CMS sees that this dependency is new.
 242   // Can probably do this lock free with some effort.
 243   ObjectLocker ol(Handle(THREAD, _list_head), THREAD);
 244 
 245   oop loader_or_mirror = new_dependency->obj_at(0);
 246 
 247   // Since the dependencies are only added, add to the end.
 248   objArrayOop end = last_handle();
 249   objArrayOop last = NULL;
 250   while (end != NULL) {
 251     last = end;
 252     // check again if another thread added it to the end.
 253     if (end->obj_at(0) == loader_or_mirror) {
 254       // Don't need to add it
 255       return;
 256     }
 257     end = (objArrayOop)end->obj_at(1);
 258   }
 259   assert (last != NULL, "dependencies should be initialized");
 260   // fill in the first element with the oop in new_dependency.
 261   if (last->obj_at(0) == NULL) {
 262     last->obj_at_put(0, new_dependency->obj_at(0));
 263   } else {
 264     last->obj_at_put(1, new_dependency());
 265   }
 266 }
 267 
 268 void ClassLoaderDataGraph::clear_claimed_marks() {
 269   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 270     cld->clear_claimed();
 271   }
 272 }
 273 
 274 void ClassLoaderData::add_class(Klass* k) {
 275   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 276   Klass* old_value = _klasses;
 277   k->set_next_link(old_value);
 278   // Make sure linked class is stable, since the class list is walked without a lock
 279   OrderAccess::storestore();
 280   // link the new item into the list
 281   _klasses = k;
 282 
 283   if (TraceClassLoaderData && Verbose && k->class_loader_data() != NULL) {
 284     ResourceMark rm;
 285     tty->print_cr("[TraceClassLoaderData] Adding k: " PTR_FORMAT " %s to CLD: "
 286                   PTR_FORMAT " loader: " PTR_FORMAT " %s",
 287                   p2i(k),
 288                   k->external_name(),
 289                   p2i(k->class_loader_data()),
 290                   p2i((void *)k->class_loader()),
 291                   loader_name());
 292   }
 293 }
 294 
 295 // This is called by InstanceKlass::deallocate_contents() to remove the
 296 // scratch_class for redefine classes.  We need a lock because there it may not
 297 // be called at a safepoint if there's an error.
 298 void ClassLoaderData::remove_class(Klass* scratch_class) {
 299   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 300   Klass* prev = NULL;
 301   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 302     if (k == scratch_class) {
 303       if (prev == NULL) {
 304         _klasses = k->next_link();
 305       } else {
 306         Klass* next = k->next_link();
 307         prev->set_next_link(next);
 308       }
 309       return;
 310     }
 311     prev = k;
 312     assert(k != k->next_link(), "no loops!");
 313   }
 314   ShouldNotReachHere();   // should have found this class!!
 315 }
 316 
 317 void ClassLoaderData::unload() {
 318   _unloading = true;
 319 
 320   // Tell serviceability tools these classes are unloading
 321   classes_do(InstanceKlass::notify_unload_class);
 322 
 323   if (TraceClassLoaderData) {
 324     ResourceMark rm;
 325     tty->print("[ClassLoaderData: unload loader data " INTPTR_FORMAT, p2i(this));
 326     tty->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)class_loader()),
 327                loader_name());
 328     if (is_anonymous()) {
 329       tty->print(" for anonymous class  " INTPTR_FORMAT " ", p2i(_klasses));
 330     }
 331     tty->print_cr("]");
 332   }
 333 }
 334 
 335 #ifdef ASSERT
 336 class AllAliveClosure : public OopClosure {
 337   BoolObjectClosure* _is_alive_closure;
 338   bool _found_dead;
 339  public:
 340   AllAliveClosure(BoolObjectClosure* is_alive_closure) : _is_alive_closure(is_alive_closure), _found_dead(false) {}
 341   template <typename T> void do_oop_work(T* p) {
 342     T heap_oop = oopDesc::load_heap_oop(p);
 343     if (!oopDesc::is_null(heap_oop)) {
 344       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
 345       if (!_is_alive_closure->do_object_b(obj)) {
 346         _found_dead = true;
 347       }
 348     }
 349   }
 350   void do_oop(oop* p)       { do_oop_work<oop>(p); }
 351   void do_oop(narrowOop* p) { do_oop_work<narrowOop>(p); }
 352   bool found_dead()         { return _found_dead; }
 353 };
 354 #endif
 355 
 356 oop ClassLoaderData::keep_alive_object() const {
 357   assert(!keep_alive(), "Don't use with CLDs that are artificially kept alive");
 358   return is_anonymous() ? _klasses->java_mirror() : class_loader();
 359 }
 360 
 361 bool ClassLoaderData::is_alive(BoolObjectClosure* is_alive_closure) const {
 362   bool alive = keep_alive() // null class loader and incomplete anonymous klasses.
 363       || is_alive_closure->do_object_b(keep_alive_object());
 364 
 365 #ifdef ASSERT
 366   if (alive) {
 367     AllAliveClosure all_alive_closure(is_alive_closure);
 368     KlassToOopClosure klass_closure(&all_alive_closure);
 369     const_cast<ClassLoaderData*>(this)->oops_do(&all_alive_closure, &klass_closure, false);
 370     assert(!all_alive_closure.found_dead(), err_msg("Found dead oop in alive cld: " PTR_FORMAT, p2i(this)));
 371   }
 372 #endif
 373 
 374   return alive;
 375 }
 376 
 377 
 378 ClassLoaderData::~ClassLoaderData() {
 379   // Release C heap structures for all the classes.
 380   classes_do(InstanceKlass::release_C_heap_structures);
 381 
 382   Metaspace *m = _metaspace;
 383   if (m != NULL) {
 384     _metaspace = NULL;
 385     // release the metaspace
 386     delete m;
 387     // release the handles
 388     if (_handles != NULL) {
 389       JNIHandleBlock::release_block(_handles);
 390       _handles = NULL;
 391     }
 392   }
 393 
 394   // Clear all the JNI handles for methods
 395   // These aren't deallocated and are going to look like a leak, but that's
 396   // needed because we can't really get rid of jmethodIDs because we don't
 397   // know when native code is going to stop using them.  The spec says that
 398   // they're "invalid" but existing programs likely rely on their being
 399   // NULL after class unloading.
 400   if (_jmethod_ids != NULL) {
 401     Method::clear_jmethod_ids(this);
 402   }
 403   // Delete lock
 404   delete _metaspace_lock;
 405 
 406   // Delete free list
 407   if (_deallocate_list != NULL) {
 408     delete _deallocate_list;
 409   }
 410 }
 411 
 412 /**
 413  * Returns true if this class loader data is for the extension class loader.
 414  */
 415 bool ClassLoaderData::is_ext_class_loader_data() const {
 416   return SystemDictionary::is_ext_class_loader(class_loader());
 417 }
 418 
 419 Metaspace* ClassLoaderData::metaspace_non_null() {
 420   assert(!DumpSharedSpaces, "wrong metaspace!");
 421   // If the metaspace has not been allocated, create a new one.  Might want
 422   // to create smaller arena for Reflection class loaders also.
 423   // The reason for the delayed allocation is because some class loaders are
 424   // simply for delegating with no metadata of their own.
 425   if (_metaspace == NULL) {
 426     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 427     // Check again if metaspace has been allocated while we were getting this lock.
 428     if (_metaspace != NULL) {
 429       return _metaspace;
 430     }
 431     if (this == the_null_class_loader_data()) {
 432       assert (class_loader() == NULL, "Must be");
 433       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType));
 434     } else if (is_anonymous()) {
 435       if (TraceClassLoaderData && Verbose && class_loader() != NULL) {
 436         tty->print_cr("is_anonymous: %s", class_loader()->klass()->internal_name());
 437       }
 438       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType));
 439     } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
 440       if (TraceClassLoaderData && Verbose && class_loader() != NULL) {
 441         tty->print_cr("is_reflection: %s", class_loader()->klass()->internal_name());
 442       }
 443       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType));
 444     } else {
 445       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType));
 446     }
 447   }
 448   return _metaspace;
 449 }
 450 
 451 JNIHandleBlock* ClassLoaderData::handles() const           { return _handles; }
 452 void ClassLoaderData::set_handles(JNIHandleBlock* handles) { _handles = handles; }
 453 
 454 jobject ClassLoaderData::add_handle(Handle h) {
 455   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 456   if (handles() == NULL) {
 457     set_handles(JNIHandleBlock::allocate_block());
 458   }
 459   return handles()->allocate_handle(h());
 460 }
 461 
 462 // Add this metadata pointer to be freed when it's safe.  This is only during
 463 // class unloading because Handles might point to this metadata field.
 464 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
 465   // Metadata in shared region isn't deleted.
 466   if (!m->is_shared()) {
 467     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 468     if (_deallocate_list == NULL) {
 469       _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, true);
 470     }
 471     _deallocate_list->append_if_missing(m);
 472   }
 473 }
 474 
 475 // Deallocate free metadata on the free list.  How useful the PermGen was!
 476 void ClassLoaderData::free_deallocate_list() {
 477   // Don't need lock, at safepoint
 478   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 479   if (_deallocate_list == NULL) {
 480     return;
 481   }
 482   // Go backwards because this removes entries that are freed.
 483   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 484     Metadata* m = _deallocate_list->at(i);
 485     if (!m->on_stack()) {
 486       _deallocate_list->remove_at(i);
 487       // There are only three types of metadata that we deallocate directly.
 488       // Cast them so they can be used by the template function.
 489       if (m->is_method()) {
 490         MetadataFactory::free_metadata(this, (Method*)m);
 491       } else if (m->is_constantPool()) {
 492         MetadataFactory::free_metadata(this, (ConstantPool*)m);
 493       } else if (m->is_klass()) {
 494         MetadataFactory::free_metadata(this, (InstanceKlass*)m);
 495       } else {
 496         ShouldNotReachHere();
 497       }
 498     }
 499   }
 500 }
 501 
 502 // These anonymous class loaders are to contain classes used for JSR292
 503 ClassLoaderData* ClassLoaderData::anonymous_class_loader_data(oop loader, TRAPS) {
 504   // Add a new class loader data to the graph.
 505   return ClassLoaderDataGraph::add(loader, true, CHECK_NULL);
 506 }
 507 
 508 const char* ClassLoaderData::loader_name() {
 509   // Handles null class loader
 510   return SystemDictionary::loader_name(class_loader());
 511 }
 512 
 513 #ifndef PRODUCT
 514 // Define to dump klasses
 515 #undef CLD_DUMP_KLASSES
 516 
 517 void ClassLoaderData::dump(outputStream * const out) {
 518   ResourceMark rm;
 519   out->print("ClassLoaderData CLD: "PTR_FORMAT", loader: "PTR_FORMAT", loader_klass: "PTR_FORMAT" %s {",
 520       p2i(this), p2i((void *)class_loader()),
 521       p2i(class_loader() != NULL ? class_loader()->klass() : NULL), loader_name());
 522   if (claimed()) out->print(" claimed ");
 523   if (is_unloading()) out->print(" unloading ");
 524   out->print(" handles " INTPTR_FORMAT, p2i(handles()));
 525   out->cr();
 526   if (metaspace_or_null() != NULL) {
 527     out->print_cr("metaspace: " INTPTR_FORMAT, p2i(metaspace_or_null()));
 528     metaspace_or_null()->dump(out);
 529   } else {
 530     out->print_cr("metaspace: NULL");
 531   }
 532 
 533 #ifdef CLD_DUMP_KLASSES
 534   if (Verbose) {
 535     ResourceMark rm;
 536     Klass* k = _klasses;
 537     while (k != NULL) {
 538       out->print_cr("klass "PTR_FORMAT", %s, CT: %d, MUT: %d", k, k->name()->as_C_string(),
 539           k->has_modified_oops(), k->has_accumulated_modified_oops());
 540       assert(k != k->next_link(), "no loops!");
 541       k = k->next_link();
 542     }
 543   }
 544 #endif  // CLD_DUMP_KLASSES
 545 #undef CLD_DUMP_KLASSES
 546   if (_jmethod_ids != NULL) {
 547     Method::print_jmethod_ids(this, out);
 548   }
 549   out->print_cr("}");
 550 }
 551 #endif // PRODUCT
 552 
 553 void ClassLoaderData::verify() {
 554   oop cl = class_loader();
 555 
 556   guarantee(this == class_loader_data(cl) || is_anonymous(), "Must be the same");
 557   guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || is_anonymous(), "must be");
 558 
 559   // Verify the integrity of the allocated space.
 560   if (metaspace_or_null() != NULL) {
 561     metaspace_or_null()->verify();
 562   }
 563 
 564   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 565     guarantee(k->class_loader_data() == this, "Must be the same");
 566     k->verify();
 567     assert(k != k->next_link(), "no loops!");
 568   }
 569 }
 570 
 571 bool ClassLoaderData::contains_klass(Klass* klass) {
 572   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 573     if (k == klass) return true;
 574   }
 575   return false;
 576 }
 577 
 578 
 579 // GC root of class loader data created.
 580 ClassLoaderData* ClassLoaderDataGraph::_head = NULL;
 581 ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
 582 ClassLoaderData* ClassLoaderDataGraph::_saved_unloading = NULL;
 583 ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
 584 
 585 bool ClassLoaderDataGraph::_should_purge = false;
 586 
 587 // Add a new class loader data node to the list.  Assign the newly created
 588 // ClassLoaderData into the java/lang/ClassLoader object as a hidden field
 589 ClassLoaderData* ClassLoaderDataGraph::add(Handle loader, bool is_anonymous, TRAPS) {
 590   // We need to allocate all the oops for the ClassLoaderData before allocating the
 591   // actual ClassLoaderData object.
 592   ClassLoaderData::Dependencies dependencies(CHECK_NULL);
 593 
 594   No_Safepoint_Verifier no_safepoints; // we mustn't GC until we've installed the
 595                                        // ClassLoaderData in the graph since the CLD
 596                                        // contains unhandled oops
 597 
 598   ClassLoaderData* cld = new ClassLoaderData(loader, is_anonymous, dependencies);
 599 
 600 
 601   if (!is_anonymous) {
 602     ClassLoaderData** cld_addr = java_lang_ClassLoader::loader_data_addr(loader());
 603     // First, Atomically set it
 604     ClassLoaderData* old = (ClassLoaderData*) Atomic::cmpxchg_ptr(cld, cld_addr, NULL);
 605     if (old != NULL) {
 606       delete cld;
 607       // Returns the data.
 608       return old;
 609     }
 610   }
 611 
 612   // We won the race, and therefore the task of adding the data to the list of
 613   // class loader data
 614   ClassLoaderData** list_head = &_head;
 615   ClassLoaderData* next = _head;
 616 
 617   do {
 618     cld->set_next(next);
 619     ClassLoaderData* exchanged = (ClassLoaderData*)Atomic::cmpxchg_ptr(cld, list_head, next);
 620     if (exchanged == next) {
 621       if (TraceClassLoaderData) {
 622         ResourceMark rm;
 623         tty->print("[ClassLoaderData: ");
 624         tty->print("create class loader data " INTPTR_FORMAT, p2i(cld));
 625         tty->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)cld->class_loader()),
 626                    cld->loader_name());
 627         tty->print_cr("]");
 628       }
 629       return cld;
 630     }
 631     next = exchanged;
 632   } while (true);
 633 
 634 }
 635 
 636 void ClassLoaderDataGraph::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 637   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 638     cld->oops_do(f, klass_closure, must_claim);
 639   }
 640 }
 641 
 642 void ClassLoaderDataGraph::keep_alive_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 643   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 644     if (cld->keep_alive()) {
 645       cld->oops_do(f, klass_closure, must_claim);
 646     }
 647   }
 648 }
 649 
 650 void ClassLoaderDataGraph::always_strong_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 651   if (ClassUnloading) {
 652     keep_alive_oops_do(f, klass_closure, must_claim);
 653   } else {
 654     oops_do(f, klass_closure, must_claim);
 655   }
 656 }
 657 
 658 void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {
 659   for (ClassLoaderData* cld = _head; cl != NULL && cld != NULL; cld = cld->next()) {
 660     cl->do_cld(cld);
 661   }
 662 }
 663 
 664 void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {
 665   for (ClassLoaderData* cld = _head;  cld != NULL; cld = cld->_next) {
 666     CLDClosure* closure = cld->keep_alive() ? strong : weak;
 667     if (closure != NULL) {
 668       closure->do_cld(cld);
 669     }
 670   }
 671 }
 672 
 673 void ClassLoaderDataGraph::keep_alive_cld_do(CLDClosure* cl) {
 674   roots_cld_do(cl, NULL);
 675 }
 676 
 677 void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
 678   if (ClassUnloading) {
 679     keep_alive_cld_do(cl);
 680   } else {
 681     cld_do(cl);
 682   }
 683 }
 684 
 685 void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
 686   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 687     cld->classes_do(klass_closure);
 688   }
 689 }
 690 
 691 void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
 692   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 693     cld->classes_do(f);
 694   }
 695 }
 696 
 697 void ClassLoaderDataGraph::methods_do(void f(Method*)) {
 698   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 699     cld->methods_do(f);
 700   }
 701 }
 702 
 703 void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
 704   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 705     cld->loaded_classes_do(klass_closure);
 706   }
 707 }
 708 
 709 void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
 710   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 711   // Only walk the head until any clds not purged from prior unloading
 712   // (CMS doesn't purge right away).
 713   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 714     cld->classes_do(f);
 715   }
 716 }
 717 
 718 GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
 719   assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
 720 
 721   GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
 722 
 723   // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
 724   ClassLoaderData* curr = _head;
 725   while (curr != _saved_head) {
 726     if (!curr->claimed()) {
 727       array->push(curr);
 728 
 729       if (TraceClassLoaderData) {
 730         tty->print("[ClassLoaderData] found new CLD: ");
 731         curr->print_value_on(tty);
 732         tty->cr();
 733       }
 734     }
 735 
 736     curr = curr->_next;
 737   }
 738 
 739   return array;
 740 }
 741 
 742 bool ClassLoaderDataGraph::unload_list_contains(const void* x) {
 743   assert(SafepointSynchronize::is_at_safepoint(), "only safe to call at safepoint");
 744   for (ClassLoaderData* cld = _unloading; cld != NULL; cld = cld->next()) {
 745     if (cld->metaspace_or_null() != NULL && cld->metaspace_or_null()->contains(x)) {
 746       return true;
 747     }
 748   }
 749   return false;
 750 }
 751 
 752 #ifndef PRODUCT
 753 bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
 754   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 755     if (loader_data == data) {
 756       return true;
 757     }
 758   }
 759 
 760   return false;
 761 }
 762 #endif // PRODUCT
 763 
 764 
 765 // Move class loader data from main list to the unloaded list for unloading
 766 // and deallocation later.
 767 bool ClassLoaderDataGraph::do_unloading(BoolObjectClosure* is_alive_closure) {
 768   ClassLoaderData* data = _head;
 769   ClassLoaderData* prev = NULL;
 770   bool seen_dead_loader = false;
 771 
 772   // Save previous _unloading pointer for CMS which may add to unloading list before
 773   // purging and we don't want to rewalk the previously unloaded class loader data.
 774   _saved_unloading = _unloading;
 775 
 776   // mark metadata seen on the stack and code cache so we can delete
 777   // unneeded entries.
 778   bool has_redefined_a_class = JvmtiExport::has_redefined_a_class();
 779   MetadataOnStackMark md_on_stack(has_redefined_a_class);
 780   if (has_redefined_a_class) {
 781     // purge_previous_versions also cleans weak method links. Because
 782     // one method's MDO can reference another method from another
 783     // class loader, we need to first clean weak method links for all
 784     // class loaders here. Below, we can then free redefined methods
 785     // for all class loaders.
 786     while (data != NULL) {
 787       if (data->is_alive(is_alive_closure)) {
 788         data->classes_do(InstanceKlass::purge_previous_versions);
 789       }
 790       data = data->next();
 791     }
 792   }
 793   data = _head;
 794   while (data != NULL) {
 795     if (data->is_alive(is_alive_closure)) {
 796       data->free_deallocate_list();
 797       prev = data;
 798       data = data->next();
 799       continue;
 800     }
 801     seen_dead_loader = true;
 802     ClassLoaderData* dead = data;
 803     dead->unload();
 804     data = data->next();
 805     // Remove from loader list.
 806     // This class loader data will no longer be found
 807     // in the ClassLoaderDataGraph.
 808     if (prev != NULL) {
 809       prev->set_next(data);
 810     } else {
 811       assert(dead == _head, "sanity check");
 812       _head = data;
 813     }
 814     dead->set_next(_unloading);
 815     _unloading = dead;
 816   }
 817 
 818   if (seen_dead_loader) {
 819     post_class_unload_events();
 820   }
 821 
 822   return seen_dead_loader;
 823 }
 824 
 825 void ClassLoaderDataGraph::purge() {
 826   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 827   ClassLoaderData* list = _unloading;
 828   _unloading = NULL;
 829   ClassLoaderData* next = list;
 830   while (next != NULL) {
 831     ClassLoaderData* purge_me = next;
 832     next = purge_me->next();
 833     delete purge_me;
 834   }
 835   Metaspace::purge();
 836 }
 837 
 838 void ClassLoaderDataGraph::post_class_unload_events(void) {
 839 #if INCLUDE_TRACE
 840   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 841   if (Tracing::enabled()) {
 842     if (Tracing::is_event_enabled(TraceClassUnloadEvent)) {
 843       assert(_unloading != NULL, "need class loader data unload list!");
 844       _class_unload_time = Ticks::now();
 845       classes_unloading_do(&class_unload_event);
 846     }
 847     Tracing::on_unloading_classes();
 848   }
 849 #endif
 850 }
 851 
 852 // CDS support
 853 
 854 // Global metaspaces for writing information to the shared archive.  When
 855 // application CDS is supported, we may need one per metaspace, so this
 856 // sort of looks like it.
 857 Metaspace* ClassLoaderData::_ro_metaspace = NULL;
 858 Metaspace* ClassLoaderData::_rw_metaspace = NULL;
 859 static bool _shared_metaspaces_initialized = false;
 860 
 861 // Initialize shared metaspaces (change to call from somewhere not lazily)
 862 void ClassLoaderData::initialize_shared_metaspaces() {
 863   assert(DumpSharedSpaces, "only use this for dumping shared spaces");
 864   assert(this == ClassLoaderData::the_null_class_loader_data(),
 865          "only supported for null loader data for now");
 866   assert (!_shared_metaspaces_initialized, "only initialize once");
 867   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 868   _ro_metaspace = new Metaspace(_metaspace_lock, Metaspace::ROMetaspaceType);
 869   _rw_metaspace = new Metaspace(_metaspace_lock, Metaspace::ReadWriteMetaspaceType);
 870   _shared_metaspaces_initialized = true;
 871 }
 872 
 873 Metaspace* ClassLoaderData::ro_metaspace() {
 874   assert(_ro_metaspace != NULL, "should already be initialized");
 875   return _ro_metaspace;
 876 }
 877 
 878 Metaspace* ClassLoaderData::rw_metaspace() {
 879   assert(_rw_metaspace != NULL, "should already be initialized");
 880   return _rw_metaspace;
 881 }
 882 
 883 ClassLoaderDataGraphKlassIteratorAtomic::ClassLoaderDataGraphKlassIteratorAtomic()
 884     : _next_klass(NULL) {
 885   ClassLoaderData* cld = ClassLoaderDataGraph::_head;
 886   Klass* klass = NULL;
 887 
 888   // Find the first klass in the CLDG.
 889   while (cld != NULL) {
 890     klass = cld->_klasses;
 891     if (klass != NULL) {
 892       _next_klass = klass;
 893       return;
 894     }
 895     cld = cld->next();
 896   }
 897 }
 898 
 899 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass_in_cldg(Klass* klass) {
 900   Klass* next = klass->next_link();
 901   if (next != NULL) {
 902     return next;
 903   }
 904 
 905   // No more klasses in the current CLD. Time to find a new CLD.
 906   ClassLoaderData* cld = klass->class_loader_data();
 907   while (next == NULL) {
 908     cld = cld->next();
 909     if (cld == NULL) {
 910       break;
 911     }
 912     next = cld->_klasses;
 913   }
 914 
 915   return next;
 916 }
 917 
 918 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass() {
 919   Klass* head = (Klass*)_next_klass;
 920 
 921   while (head != NULL) {
 922     Klass* next = next_klass_in_cldg(head);
 923 
 924     Klass* old_head = (Klass*)Atomic::cmpxchg_ptr(next, &_next_klass, head);
 925 
 926     if (old_head == head) {
 927       return head; // Won the CAS.
 928     }
 929 
 930     head = old_head;
 931   }
 932 
 933   // Nothing more for the iterator to hand out.
 934   assert(head == NULL, err_msg("head is " PTR_FORMAT ", expected not null:", p2i(head)));
 935   return NULL;
 936 }
 937 
 938 ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
 939   _data = ClassLoaderDataGraph::_head;
 940 }
 941 
 942 ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
 943 
 944 #ifndef PRODUCT
 945 // callable from debugger
 946 extern "C" int print_loader_data_graph() {
 947   ClassLoaderDataGraph::dump_on(tty);
 948   return 0;
 949 }
 950 
 951 void ClassLoaderDataGraph::verify() {
 952   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 953     data->verify();
 954   }
 955 }
 956 
 957 void ClassLoaderDataGraph::dump_on(outputStream * const out) {
 958   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 959     data->dump(out);
 960   }
 961   MetaspaceAux::dump(out);
 962 }
 963 #endif // PRODUCT
 964 
 965 void ClassLoaderData::print_value_on(outputStream* out) const {
 966   if (class_loader() == NULL) {
 967     out->print("NULL class_loader");
 968   } else {
 969     out->print("class loader " INTPTR_FORMAT, p2i(this));
 970     class_loader()->print_value_on(out);
 971   }
 972 }
 973 
 974 #if INCLUDE_TRACE
 975 
 976 Ticks ClassLoaderDataGraph::_class_unload_time;
 977 
 978 void ClassLoaderDataGraph::class_unload_event(Klass* const k) {
 979 
 980   // post class unload event
 981   EventClassUnload event(UNTIMED);
 982   event.set_endtime(_class_unload_time);
 983   event.set_unloadedClass(k);
 984   oop defining_class_loader = k->class_loader();
 985   event.set_definingClassLoader(defining_class_loader != NULL ?
 986                                 defining_class_loader->klass() : (Klass*)NULL);
 987   event.commit();
 988 }
 989 
 990 #endif /* INCLUDE_TRACE */