1 /*
   2  * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // A ClassLoaderData identifies the full set of class types that a class
  26 // loader's name resolution strategy produces for a given configuration of the
  27 // class loader.
  28 // Class types in the ClassLoaderData may be defined by from class file binaries
  29 // provided by the class loader, or from other class loader it interacts with
  30 // according to its name resolution strategy.
  31 //
  32 // Class loaders that implement a deterministic name resolution strategy
  33 // (including with respect to their delegation behavior), such as the boot, the
  34 // 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 "gc/shared/gcLocker.hpp"
  57 #include "logging/log.hpp"
  58 #include "memory/metadataFactory.hpp"
  59 #include "memory/metaspaceShared.hpp"
  60 #include "memory/oopFactory.hpp"
  61 #include "memory/resourceArea.hpp"
  62 #include "oops/objArrayOop.inline.hpp"
  63 #include "oops/oop.inline.hpp"
  64 #include "runtime/atomic.inline.hpp"
  65 #include "runtime/javaCalls.hpp"
  66 #include "runtime/jniHandles.hpp"
  67 #include "runtime/mutex.hpp"
  68 #include "runtime/safepoint.hpp"
  69 #include "runtime/synchronizer.hpp"
  70 #include "utilities/growableArray.hpp"
  71 #include "utilities/macros.hpp"
  72 #include "utilities/ostream.hpp"
  73 #if INCLUDE_TRACE
  74 #include "trace/tracing.hpp"
  75 #endif
  76 
  77 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
  78 
  79 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies) :
  80   _class_loader(h_class_loader()),
  81   _is_anonymous(is_anonymous),
  82   // An anonymous class loader data doesn't have anything to keep
  83   // it from being unloaded during parsing of the anonymous class.
  84   // The null-class-loader should always be kept alive.
  85   _keep_alive(is_anonymous || h_class_loader.is_null()),
  86   _metaspace(NULL), _unloading(false), _klasses(NULL),
  87   _claimed(0), _jmethod_ids(NULL), _handles(NULL), _deallocate_list(NULL),
  88   _next(NULL), _dependencies(dependencies), _shared_class_loader_id(-1),
  89   _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true,
  90                             Monitor::_safepoint_check_never)) {
  91     // empty
  92 }
  93 
  94 void ClassLoaderData::init_dependencies(TRAPS) {
  95   assert(!Universe::is_fully_initialized(), "should only be called when initializing");
  96   assert(is_the_null_class_loader_data(), "should only call this for the null class loader");
  97   _dependencies.init(CHECK);
  98 }
  99 
 100 void ClassLoaderData::Dependencies::init(TRAPS) {
 101   // Create empty dependencies array to add to. CMS requires this to be
 102   // an oop so that it can track additions via card marks.  We think.
 103   _list_head = oopFactory::new_objectArray(2, CHECK);
 104 }
 105 
 106 bool ClassLoaderData::claim() {
 107   if (_claimed == 1) {
 108     return false;
 109   }
 110 
 111   return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;
 112 }
 113 
 114 void ClassLoaderData::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 115   if (must_claim && !claim()) {
 116     return;
 117   }
 118 
 119   f->do_oop(&_class_loader);
 120   _dependencies.oops_do(f);
 121   _handles->oops_do(f);
 122   if (klass_closure != NULL) {
 123     classes_do(klass_closure);
 124   }
 125 }
 126 
 127 void ClassLoaderData::Dependencies::oops_do(OopClosure* f) {
 128   f->do_oop((oop*)&_list_head);
 129 }
 130 
 131 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
 132   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 133     klass_closure->do_klass(k);
 134     assert(k != k->next_link(), "no loops!");
 135   }
 136 }
 137 
 138 void ClassLoaderData::classes_do(void f(Klass * const)) {
 139   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 140     f(k);
 141   }
 142 }
 143 
 144 void ClassLoaderData::methods_do(void f(Method*)) {
 145   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 146     if (k->is_instance_klass()) {
 147       InstanceKlass::cast(k)->methods_do(f);
 148     }
 149   }
 150 }
 151 
 152 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
 153   // Lock to avoid classes being modified/added/removed during iteration
 154   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 155   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 156     // Do not filter ArrayKlass oops here...
 157     if (k->is_array_klass() || (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded())) {
 158       klass_closure->do_klass(k);
 159     }
 160   }
 161 }
 162 
 163 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
 164   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 165     if (k->is_instance_klass()) {
 166       f(InstanceKlass::cast(k));
 167     }
 168     assert(k != k->next_link(), "no loops!");
 169   }
 170 }
 171 
 172 void ClassLoaderData::record_dependency(const Klass* k, TRAPS) {
 173   assert(k != NULL, "invariant");
 174 
 175   ClassLoaderData * const from_cld = this;
 176   ClassLoaderData * const to_cld = k->class_loader_data();
 177 
 178   // Dependency to the null class loader data doesn't need to be recorded
 179   // because the null class loader data never goes away.
 180   if (to_cld->is_the_null_class_loader_data()) {
 181     return;
 182   }
 183 
 184   oop to;
 185   if (to_cld->is_anonymous()) {
 186     // Anonymous class dependencies are through the mirror.
 187     to = k->java_mirror();
 188   } else {
 189     to = to_cld->class_loader();
 190 
 191     // If from_cld is anonymous, even if it's class_loader is a parent of 'to'
 192     // we still have to add it.  The class_loader won't keep from_cld alive.
 193     if (!from_cld->is_anonymous()) {
 194       // Check that this dependency isn't from the same or parent class_loader
 195       oop from = from_cld->class_loader();
 196 
 197       oop curr = from;
 198       while (curr != NULL) {
 199         if (curr == to) {
 200           return; // this class loader is in the parent list, no need to add it.
 201         }
 202         curr = java_lang_ClassLoader::parent(curr);
 203       }
 204     }
 205   }
 206 
 207   // It's a dependency we won't find through GC, add it. This is relatively rare
 208   // Must handle over GC point.
 209   Handle dependency(THREAD, to);
 210   from_cld->_dependencies.add(dependency, CHECK);
 211 }
 212 
 213 
 214 void ClassLoaderData::Dependencies::add(Handle dependency, TRAPS) {
 215   // Check first if this dependency is already in the list.
 216   // Save a pointer to the last to add to under the lock.
 217   objArrayOop ok = _list_head;
 218   objArrayOop last = NULL;
 219   while (ok != NULL) {
 220     last = ok;
 221     if (ok->obj_at(0) == dependency()) {
 222       // Don't need to add it
 223       return;
 224     }
 225     ok = (objArrayOop)ok->obj_at(1);
 226   }
 227 
 228   // Must handle over GC points
 229   assert (last != NULL, "dependencies should be initialized");
 230   objArrayHandle last_handle(THREAD, last);
 231 
 232   // Create a new dependency node with fields for (class_loader or mirror, next)
 233   objArrayOop deps = oopFactory::new_objectArray(2, CHECK);
 234   deps->obj_at_put(0, dependency());
 235 
 236   // Must handle over GC points
 237   objArrayHandle new_dependency(THREAD, deps);
 238 
 239   // Add the dependency under lock
 240   locked_add(last_handle, new_dependency, THREAD);
 241 }
 242 
 243 void ClassLoaderData::Dependencies::locked_add(objArrayHandle last_handle,
 244                                                objArrayHandle new_dependency,
 245                                                Thread* THREAD) {
 246 
 247   // Have to lock and put the new dependency on the end of the dependency
 248   // array so the card mark for CMS sees that this dependency is new.
 249   // Can probably do this lock free with some effort.
 250   ObjectLocker ol(Handle(THREAD, _list_head), THREAD);
 251 
 252   oop loader_or_mirror = new_dependency->obj_at(0);
 253 
 254   // Since the dependencies are only added, add to the end.
 255   objArrayOop end = last_handle();
 256   objArrayOop last = NULL;
 257   while (end != NULL) {
 258     last = end;
 259     // check again if another thread added it to the end.
 260     if (end->obj_at(0) == loader_or_mirror) {
 261       // Don't need to add it
 262       return;
 263     }
 264     end = (objArrayOop)end->obj_at(1);
 265   }
 266   assert (last != NULL, "dependencies should be initialized");
 267   // fill in the first element with the oop in new_dependency.
 268   if (last->obj_at(0) == NULL) {
 269     last->obj_at_put(0, new_dependency->obj_at(0));
 270   } else {
 271     last->obj_at_put(1, new_dependency());
 272   }
 273 }
 274 
 275 void ClassLoaderDataGraph::clear_claimed_marks() {
 276   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 277     cld->clear_claimed();
 278   }
 279 }
 280 
 281 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
 282   {
 283     MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 284     Klass* old_value = _klasses;
 285     k->set_next_link(old_value);
 286     // Make sure linked class is stable, since the class list is walked without a lock
 287     OrderAccess::storestore();
 288     // link the new item into the list
 289     _klasses = k;
 290   }
 291 
 292   if (publicize && k->class_loader_data() != NULL) {
 293     ResourceMark rm;
 294     log_trace(classloaderdata)("Adding k: " PTR_FORMAT " %s to CLD: "
 295                   PTR_FORMAT " loader: " PTR_FORMAT " %s",
 296                   p2i(k),
 297                   k->external_name(),
 298                   p2i(k->class_loader_data()),
 299                   p2i((void *)k->class_loader()),
 300                   loader_name());
 301   }
 302 }
 303 
 304 // This is called by InstanceKlass::deallocate_contents() to remove the
 305 // scratch_class for redefine classes.  We need a lock because there it may not
 306 // be called at a safepoint if there's an error.
 307 void ClassLoaderData::remove_class(Klass* scratch_class) {
 308   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 309   Klass* prev = NULL;
 310   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 311     if (k == scratch_class) {
 312       if (prev == NULL) {
 313         _klasses = k->next_link();
 314       } else {
 315         Klass* next = k->next_link();
 316         prev->set_next_link(next);
 317       }
 318       return;
 319     }
 320     prev = k;
 321     assert(k != k->next_link(), "no loops!");
 322   }
 323   ShouldNotReachHere();   // should have found this class!!
 324 }
 325 
 326 void ClassLoaderData::unload() {
 327   _unloading = true;
 328 
 329   // Tell serviceability tools these classes are unloading
 330   classes_do(InstanceKlass::notify_unload_class);
 331 
 332   if (log_is_enabled(Debug, classloaderdata)) {
 333     ResourceMark rm;
 334     outputStream* log = LogHandle(classloaderdata)::debug_stream();
 335     log->print(": unload loader data " INTPTR_FORMAT, p2i(this));
 336     log->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)class_loader()),
 337                loader_name());
 338     if (is_anonymous()) {
 339       log->print(" for anonymous class  " INTPTR_FORMAT " ", p2i(_klasses));
 340     }
 341     log->cr();
 342   }
 343 }
 344 
 345 oop ClassLoaderData::keep_alive_object() const {
 346   assert(!keep_alive(), "Don't use with CLDs that are artificially kept alive");
 347   return is_anonymous() ? _klasses->java_mirror() : class_loader();
 348 }
 349 
 350 bool ClassLoaderData::is_alive(BoolObjectClosure* is_alive_closure) const {
 351   bool alive = keep_alive() // null class loader and incomplete anonymous klasses.
 352       || is_alive_closure->do_object_b(keep_alive_object());
 353 
 354   return alive;
 355 }
 356 
 357 
 358 ClassLoaderData::~ClassLoaderData() {
 359   // Release C heap structures for all the classes.
 360   classes_do(InstanceKlass::release_C_heap_structures);
 361 
 362   Metaspace *m = _metaspace;
 363   if (m != NULL) {
 364     _metaspace = NULL;
 365     // release the metaspace
 366     delete m;
 367     // release the handles
 368     if (_handles != NULL) {
 369       JNIHandleBlock::release_block(_handles);
 370       _handles = NULL;
 371     }
 372   }
 373 
 374   // Clear all the JNI handles for methods
 375   // These aren't deallocated and are going to look like a leak, but that's
 376   // needed because we can't really get rid of jmethodIDs because we don't
 377   // know when native code is going to stop using them.  The spec says that
 378   // they're "invalid" but existing programs likely rely on their being
 379   // NULL after class unloading.
 380   if (_jmethod_ids != NULL) {
 381     Method::clear_jmethod_ids(this);
 382   }
 383   // Delete lock
 384   delete _metaspace_lock;
 385 
 386   // Delete free list
 387   if (_deallocate_list != NULL) {
 388     delete _deallocate_list;
 389   }
 390 }
 391 
 392 /**
 393  * Returns true if this class loader data is for the extension class loader.
 394  */
 395 bool ClassLoaderData::is_ext_class_loader_data() const {
 396   return SystemDictionary::is_ext_class_loader(class_loader());
 397 }
 398 
 399 Metaspace* ClassLoaderData::metaspace_non_null() {
 400   assert(!DumpSharedSpaces, "wrong metaspace!");
 401   // If the metaspace has not been allocated, create a new one.  Might want
 402   // to create smaller arena for Reflection class loaders also.
 403   // The reason for the delayed allocation is because some class loaders are
 404   // simply for delegating with no metadata of their own.
 405   if (_metaspace == NULL) {
 406     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 407     // Check again if metaspace has been allocated while we were getting this lock.
 408     if (_metaspace != NULL) {
 409       return _metaspace;
 410     }
 411     if (this == the_null_class_loader_data()) {
 412       assert (class_loader() == NULL, "Must be");
 413       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType));
 414     } else if (is_anonymous()) {
 415       if (class_loader() != NULL) {
 416         log_trace(classloaderdata)("is_anonymous: %s", class_loader()->klass()->internal_name());
 417       }
 418       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType));
 419     } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
 420       if (class_loader() != NULL) {
 421         log_trace(classloaderdata)("is_reflection: %s", class_loader()->klass()->internal_name());
 422       }
 423       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType));
 424     } else {
 425       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType));
 426     }
 427   }
 428   return _metaspace;
 429 }
 430 
 431 JNIHandleBlock* ClassLoaderData::handles() const           { return _handles; }
 432 void ClassLoaderData::set_handles(JNIHandleBlock* handles) { _handles = handles; }
 433 
 434 jobject ClassLoaderData::add_handle(Handle h) {
 435   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 436   if (handles() == NULL) {
 437     set_handles(JNIHandleBlock::allocate_block());
 438   }
 439   return handles()->allocate_handle(h());
 440 }
 441 
 442 // Add this metadata pointer to be freed when it's safe.  This is only during
 443 // class unloading because Handles might point to this metadata field.
 444 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
 445   // Metadata in shared region isn't deleted.
 446   if (!m->is_shared()) {
 447     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 448     if (_deallocate_list == NULL) {
 449       _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, true);
 450     }
 451     _deallocate_list->append_if_missing(m);
 452   }
 453 }
 454 
 455 // Deallocate free metadata on the free list.  How useful the PermGen was!
 456 void ClassLoaderData::free_deallocate_list() {
 457   // Don't need lock, at safepoint
 458   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 459   if (_deallocate_list == NULL) {
 460     return;
 461   }
 462   // Go backwards because this removes entries that are freed.
 463   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 464     Metadata* m = _deallocate_list->at(i);
 465     if (!m->on_stack()) {
 466       _deallocate_list->remove_at(i);
 467       // There are only three types of metadata that we deallocate directly.
 468       // Cast them so they can be used by the template function.
 469       if (m->is_method()) {
 470         MetadataFactory::free_metadata(this, (Method*)m);
 471       } else if (m->is_constantPool()) {
 472         MetadataFactory::free_metadata(this, (ConstantPool*)m);
 473       } else if (m->is_klass()) {
 474         MetadataFactory::free_metadata(this, (InstanceKlass*)m);
 475       } else {
 476         ShouldNotReachHere();
 477       }
 478     } else {
 479       // Metadata is alive.
 480       // If scratch_class is on stack then it shouldn't be on this list!
 481       assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
 482              "scratch classes on this list should be dead");
 483       // Also should assert that other metadata on the list was found in handles.
 484     }
 485   }
 486 }
 487 
 488 // These anonymous class loaders are to contain classes used for JSR292
 489 ClassLoaderData* ClassLoaderData::anonymous_class_loader_data(oop loader, TRAPS) {
 490   // Add a new class loader data to the graph.
 491   return ClassLoaderDataGraph::add(loader, true, THREAD);
 492 }
 493 
 494 const char* ClassLoaderData::loader_name() {
 495   // Handles null class loader
 496   return SystemDictionary::loader_name(class_loader());
 497 }
 498 
 499 #ifndef PRODUCT
 500 // Define to dump klasses
 501 #undef CLD_DUMP_KLASSES
 502 
 503 void ClassLoaderData::dump(outputStream * const out) {
 504   ResourceMark rm;
 505   out->print("ClassLoaderData CLD: " PTR_FORMAT ", loader: " PTR_FORMAT ", loader_klass: " PTR_FORMAT " %s {",
 506       p2i(this), p2i((void *)class_loader()),
 507       p2i(class_loader() != NULL ? class_loader()->klass() : NULL), loader_name());
 508   if (claimed()) out->print(" claimed ");
 509   if (is_unloading()) out->print(" unloading ");
 510   out->print(" handles " INTPTR_FORMAT, p2i(handles()));
 511   out->cr();
 512   if (metaspace_or_null() != NULL) {
 513     out->print_cr("metaspace: " INTPTR_FORMAT, p2i(metaspace_or_null()));
 514     metaspace_or_null()->dump(out);
 515   } else {
 516     out->print_cr("metaspace: NULL");
 517   }
 518 
 519 #ifdef CLD_DUMP_KLASSES
 520   if (Verbose) {
 521     ResourceMark rm;
 522     Klass* k = _klasses;
 523     while (k != NULL) {
 524       out->print_cr("klass " PTR_FORMAT ", %s, CT: %d, MUT: %d", k, k->name()->as_C_string(),
 525           k->has_modified_oops(), k->has_accumulated_modified_oops());
 526       assert(k != k->next_link(), "no loops!");
 527       k = k->next_link();
 528     }
 529   }
 530 #endif  // CLD_DUMP_KLASSES
 531 #undef CLD_DUMP_KLASSES
 532   if (_jmethod_ids != NULL) {
 533     Method::print_jmethod_ids(this, out);
 534   }
 535   out->print_cr("}");
 536 }
 537 #endif // PRODUCT
 538 
 539 void ClassLoaderData::verify() {
 540   oop cl = class_loader();
 541 
 542   guarantee(this == class_loader_data(cl) || is_anonymous(), "Must be the same");
 543   guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || is_anonymous(), "must be");
 544 
 545   // Verify the integrity of the allocated space.
 546   if (metaspace_or_null() != NULL) {
 547     metaspace_or_null()->verify();
 548   }
 549 
 550   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 551     guarantee(k->class_loader_data() == this, "Must be the same");
 552     k->verify();
 553     assert(k != k->next_link(), "no loops!");
 554   }
 555 }
 556 
 557 bool ClassLoaderData::contains_klass(Klass* klass) {
 558   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 559     if (k == klass) return true;
 560   }
 561   return false;
 562 }
 563 
 564 
 565 // GC root of class loader data created.
 566 ClassLoaderData* ClassLoaderDataGraph::_head = NULL;
 567 ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
 568 ClassLoaderData* ClassLoaderDataGraph::_saved_unloading = NULL;
 569 ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
 570 
 571 bool ClassLoaderDataGraph::_should_purge = false;
 572 bool ClassLoaderDataGraph::_metaspace_oom = false;
 573 
 574 // Add a new class loader data node to the list.  Assign the newly created
 575 // ClassLoaderData into the java/lang/ClassLoader object as a hidden field
 576 ClassLoaderData* ClassLoaderDataGraph::add(Handle loader, bool is_anonymous, TRAPS) {
 577   // We need to allocate all the oops for the ClassLoaderData before allocating the
 578   // actual ClassLoaderData object.
 579   ClassLoaderData::Dependencies dependencies(CHECK_NULL);
 580 
 581   NoSafepointVerifier no_safepoints; // we mustn't GC until we've installed the
 582                                      // ClassLoaderData in the graph since the CLD
 583                                      // contains unhandled oops
 584 
 585   ClassLoaderData* cld = new ClassLoaderData(loader, is_anonymous, dependencies);
 586 
 587 
 588   if (!is_anonymous) {
 589     ClassLoaderData** cld_addr = java_lang_ClassLoader::loader_data_addr(loader());
 590     // First, Atomically set it
 591     ClassLoaderData* old = (ClassLoaderData*) Atomic::cmpxchg_ptr(cld, cld_addr, NULL);
 592     if (old != NULL) {
 593       delete cld;
 594       // Returns the data.
 595       return old;
 596     }
 597   }
 598 
 599   // We won the race, and therefore the task of adding the data to the list of
 600   // class loader data
 601   ClassLoaderData** list_head = &_head;
 602   ClassLoaderData* next = _head;
 603 
 604   do {
 605     cld->set_next(next);
 606     ClassLoaderData* exchanged = (ClassLoaderData*)Atomic::cmpxchg_ptr(cld, list_head, next);
 607     if (exchanged == next) {
 608       if (log_is_enabled(Debug, classloaderdata)) {
 609        PauseNoSafepointVerifier pnsv(&no_safepoints); // Need safe points for JavaCalls::call_virtual
 610        log_creation(loader, cld, CHECK_NULL);
 611       }
 612       return cld;
 613     }
 614     next = exchanged;
 615   } while (true);
 616 }
 617 
 618 void ClassLoaderDataGraph::log_creation(Handle loader, ClassLoaderData* cld, TRAPS) {
 619   Handle string;
 620   if (loader.not_null()) {
 621     // Include the result of loader.toString() in the output. This allows
 622     // the user of the log to identify the class loader instance.
 623     JavaValue result(T_OBJECT);
 624     KlassHandle spec_klass(THREAD, SystemDictionary::ClassLoader_klass());
 625     JavaCalls::call_virtual(&result,
 626                             loader,
 627                             spec_klass,
 628                             vmSymbols::toString_name(),
 629                             vmSymbols::void_string_signature(),
 630                             CHECK);
 631     assert(result.get_type() == T_OBJECT, "just checking");
 632     string = (oop)result.get_jobject();
 633   }
 634 
 635   ResourceMark rm;
 636   outputStream* log = LogHandle(classloaderdata)::debug_stream();
 637   log->print("create class loader data " INTPTR_FORMAT, p2i(cld));
 638   log->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)cld->class_loader()),
 639              cld->loader_name());
 640 
 641   if (string.not_null()) {
 642     log->print(": ");
 643     java_lang_String::print(string(), log);
 644   }
 645   log->cr();
 646 }
 647 
 648 
 649 void ClassLoaderDataGraph::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 650   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 651     cld->oops_do(f, klass_closure, must_claim);
 652   }
 653 }
 654 
 655 void ClassLoaderDataGraph::keep_alive_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 656   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 657     if (cld->keep_alive()) {
 658       cld->oops_do(f, klass_closure, must_claim);
 659     }
 660   }
 661 }
 662 
 663 void ClassLoaderDataGraph::always_strong_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 664   if (ClassUnloading) {
 665     keep_alive_oops_do(f, klass_closure, must_claim);
 666   } else {
 667     oops_do(f, klass_closure, must_claim);
 668   }
 669 }
 670 
 671 void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {
 672   for (ClassLoaderData* cld = _head; cl != NULL && cld != NULL; cld = cld->next()) {
 673     cl->do_cld(cld);
 674   }
 675 }
 676 
 677 void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {
 678   for (ClassLoaderData* cld = _head;  cld != NULL; cld = cld->_next) {
 679     CLDClosure* closure = cld->keep_alive() ? strong : weak;
 680     if (closure != NULL) {
 681       closure->do_cld(cld);
 682     }
 683   }
 684 }
 685 
 686 void ClassLoaderDataGraph::keep_alive_cld_do(CLDClosure* cl) {
 687   roots_cld_do(cl, NULL);
 688 }
 689 
 690 void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
 691   if (ClassUnloading) {
 692     keep_alive_cld_do(cl);
 693   } else {
 694     cld_do(cl);
 695   }
 696 }
 697 
 698 void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
 699   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 700     cld->classes_do(klass_closure);
 701   }
 702 }
 703 
 704 void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
 705   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 706     cld->classes_do(f);
 707   }
 708 }
 709 
 710 void ClassLoaderDataGraph::methods_do(void f(Method*)) {
 711   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 712     cld->methods_do(f);
 713   }
 714 }
 715 
 716 void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
 717   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 718     cld->loaded_classes_do(klass_closure);
 719   }
 720 }
 721 
 722 void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
 723   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 724   // Only walk the head until any clds not purged from prior unloading
 725   // (CMS doesn't purge right away).
 726   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 727     cld->classes_do(f);
 728   }
 729 }
 730 
 731 GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
 732   assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
 733 
 734   GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
 735 
 736   // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
 737   ClassLoaderData* curr = _head;
 738   while (curr != _saved_head) {
 739     if (!curr->claimed()) {
 740       array->push(curr);
 741 
 742       if (log_is_enabled(Debug, classloaderdata)) {
 743         outputStream* log = LogHandle(classloaderdata)::debug_stream();
 744         log->print("found new CLD: ");
 745         curr->print_value_on(log);
 746         log->cr();
 747       }
 748     }
 749 
 750     curr = curr->_next;
 751   }
 752 
 753   return array;
 754 }
 755 
 756 bool ClassLoaderDataGraph::unload_list_contains(const void* x) {
 757   assert(SafepointSynchronize::is_at_safepoint(), "only safe to call at safepoint");
 758   for (ClassLoaderData* cld = _unloading; cld != NULL; cld = cld->next()) {
 759     if (cld->metaspace_or_null() != NULL && cld->metaspace_or_null()->contains(x)) {
 760       return true;
 761     }
 762   }
 763   return false;
 764 }
 765 
 766 #ifndef PRODUCT
 767 bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
 768   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 769     if (loader_data == data) {
 770       return true;
 771     }
 772   }
 773 
 774   return false;
 775 }
 776 #endif // PRODUCT
 777 
 778 
 779 // Move class loader data from main list to the unloaded list for unloading
 780 // and deallocation later.
 781 bool ClassLoaderDataGraph::do_unloading(BoolObjectClosure* is_alive_closure,
 782                                         bool clean_previous_versions) {
 783 
 784   ClassLoaderData* data = _head;
 785   ClassLoaderData* prev = NULL;
 786   bool seen_dead_loader = false;
 787 
 788   // Mark metadata seen on the stack only so we can delete unneeded entries.
 789   // Only walk all metadata, including the expensive code cache walk, for Full GC
 790   // and only if class redefinition and if there's previous versions of
 791   // Klasses to delete.
 792   bool walk_all_metadata = clean_previous_versions &&
 793                            JvmtiExport::has_redefined_a_class() &&
 794                            InstanceKlass::has_previous_versions();
 795   MetadataOnStackMark md_on_stack(walk_all_metadata);
 796 
 797   // Save previous _unloading pointer for CMS which may add to unloading list before
 798   // purging and we don't want to rewalk the previously unloaded class loader data.
 799   _saved_unloading = _unloading;
 800 
 801   data = _head;
 802   while (data != NULL) {
 803     if (data->is_alive(is_alive_closure)) {
 804       // clean metaspace
 805       if (walk_all_metadata) {
 806         data->classes_do(InstanceKlass::purge_previous_versions);
 807       }
 808       data->free_deallocate_list();
 809       prev = data;
 810       data = data->next();
 811       continue;
 812     }
 813     seen_dead_loader = true;
 814     ClassLoaderData* dead = data;
 815     dead->unload();
 816     data = data->next();
 817     // Remove from loader list.
 818     // This class loader data will no longer be found
 819     // in the ClassLoaderDataGraph.
 820     if (prev != NULL) {
 821       prev->set_next(data);
 822     } else {
 823       assert(dead == _head, "sanity check");
 824       _head = data;
 825     }
 826     dead->set_next(_unloading);
 827     _unloading = dead;
 828   }
 829 
 830   if (seen_dead_loader) {
 831     post_class_unload_events();
 832   }
 833 
 834   return seen_dead_loader;
 835 }
 836 
 837 void ClassLoaderDataGraph::purge() {
 838   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 839   ClassLoaderData* list = _unloading;
 840   _unloading = NULL;
 841   ClassLoaderData* next = list;
 842   bool classes_unloaded = false;
 843   while (next != NULL) {
 844     ClassLoaderData* purge_me = next;
 845     next = purge_me->next();
 846     delete purge_me;
 847     classes_unloaded = true;
 848   }
 849   if (classes_unloaded) {
 850     Metaspace::purge();
 851     set_metaspace_oom(false);
 852   }
 853 }
 854 
 855 void ClassLoaderDataGraph::post_class_unload_events(void) {
 856 #if INCLUDE_TRACE
 857   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 858   if (Tracing::enabled()) {
 859     if (Tracing::is_event_enabled(TraceClassUnloadEvent)) {
 860       assert(_unloading != NULL, "need class loader data unload list!");
 861       _class_unload_time = Ticks::now();
 862       classes_unloading_do(&class_unload_event);
 863     }
 864     Tracing::on_unloading_classes();
 865   }
 866 #endif
 867 }
 868 
 869 // CDS support
 870 
 871 // Global metaspaces for writing information to the shared archive.  When
 872 // application CDS is supported, we may need one per metaspace, so this
 873 // sort of looks like it.
 874 Metaspace* ClassLoaderData::_ro_metaspace = NULL;
 875 Metaspace* ClassLoaderData::_rw_metaspace = NULL;
 876 static bool _shared_metaspaces_initialized = false;
 877 
 878 // Initialize shared metaspaces (change to call from somewhere not lazily)
 879 void ClassLoaderData::initialize_shared_metaspaces() {
 880   assert(DumpSharedSpaces, "only use this for dumping shared spaces");
 881   assert(this == ClassLoaderData::the_null_class_loader_data(),
 882          "only supported for null loader data for now");
 883   assert (!_shared_metaspaces_initialized, "only initialize once");
 884   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 885   _ro_metaspace = new Metaspace(_metaspace_lock, Metaspace::ROMetaspaceType);
 886   _rw_metaspace = new Metaspace(_metaspace_lock, Metaspace::ReadWriteMetaspaceType);
 887   _shared_metaspaces_initialized = true;
 888 }
 889 
 890 Metaspace* ClassLoaderData::ro_metaspace() {
 891   assert(_ro_metaspace != NULL, "should already be initialized");
 892   return _ro_metaspace;
 893 }
 894 
 895 Metaspace* ClassLoaderData::rw_metaspace() {
 896   assert(_rw_metaspace != NULL, "should already be initialized");
 897   return _rw_metaspace;
 898 }
 899 
 900 ClassLoaderDataGraphKlassIteratorAtomic::ClassLoaderDataGraphKlassIteratorAtomic()
 901     : _next_klass(NULL) {
 902   ClassLoaderData* cld = ClassLoaderDataGraph::_head;
 903   Klass* klass = NULL;
 904 
 905   // Find the first klass in the CLDG.
 906   while (cld != NULL) {
 907     klass = cld->_klasses;
 908     if (klass != NULL) {
 909       _next_klass = klass;
 910       return;
 911     }
 912     cld = cld->next();
 913   }
 914 }
 915 
 916 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass_in_cldg(Klass* klass) {
 917   Klass* next = klass->next_link();
 918   if (next != NULL) {
 919     return next;
 920   }
 921 
 922   // No more klasses in the current CLD. Time to find a new CLD.
 923   ClassLoaderData* cld = klass->class_loader_data();
 924   while (next == NULL) {
 925     cld = cld->next();
 926     if (cld == NULL) {
 927       break;
 928     }
 929     next = cld->_klasses;
 930   }
 931 
 932   return next;
 933 }
 934 
 935 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass() {
 936   Klass* head = _next_klass;
 937 
 938   while (head != NULL) {
 939     Klass* next = next_klass_in_cldg(head);
 940 
 941     Klass* old_head = (Klass*)Atomic::cmpxchg_ptr(next, &_next_klass, head);
 942 
 943     if (old_head == head) {
 944       return head; // Won the CAS.
 945     }
 946 
 947     head = old_head;
 948   }
 949 
 950   // Nothing more for the iterator to hand out.
 951   assert(head == NULL, "head is " PTR_FORMAT ", expected not null:", p2i(head));
 952   return NULL;
 953 }
 954 
 955 ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
 956   _data = ClassLoaderDataGraph::_head;
 957 }
 958 
 959 ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
 960 
 961 #ifndef PRODUCT
 962 // callable from debugger
 963 extern "C" int print_loader_data_graph() {
 964   ClassLoaderDataGraph::dump_on(tty);
 965   return 0;
 966 }
 967 
 968 void ClassLoaderDataGraph::verify() {
 969   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 970     data->verify();
 971   }
 972 }
 973 
 974 void ClassLoaderDataGraph::dump_on(outputStream * const out) {
 975   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 976     data->dump(out);
 977   }
 978   MetaspaceAux::dump(out);
 979 }
 980 #endif // PRODUCT
 981 
 982 void ClassLoaderData::print_value_on(outputStream* out) const {
 983   if (class_loader() == NULL) {
 984     out->print("NULL class_loader");
 985   } else {
 986     out->print("class loader " INTPTR_FORMAT, p2i(this));
 987     class_loader()->print_value_on(out);
 988   }
 989 }
 990 
 991 #if INCLUDE_TRACE
 992 
 993 Ticks ClassLoaderDataGraph::_class_unload_time;
 994 
 995 void ClassLoaderDataGraph::class_unload_event(Klass* const k) {
 996 
 997   // post class unload event
 998   EventClassUnload event(UNTIMED);
 999   event.set_endtime(_class_unload_time);
1000   event.set_unloadedClass(k);
1001   oop defining_class_loader = k->class_loader();
1002   event.set_definingClassLoader(defining_class_loader != NULL ?
1003                                 defining_class_loader->klass() : (Klass*)NULL);
1004   event.commit();
1005 }
1006 
1007 #endif // INCLUDE_TRACE
--- EOF ---