rev 7903 : fix volatile qualifier ClassLoaderDataGraphKlassIteratorAtomic::next_klass

   1 /*
   2  * Copyright (c) 2012, 2015, 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 "oops/objArrayOop.inline.hpp"
  61 #include "oops/oop.inline.hpp"
  62 #include "runtime/atomic.inline.hpp"
  63 #include "runtime/jniHandles.hpp"
  64 #include "runtime/mutex.hpp"
  65 #include "runtime/safepoint.hpp"
  66 #include "runtime/synchronizer.hpp"
  67 #include "utilities/growableArray.hpp"
  68 #include "utilities/macros.hpp"
  69 #include "utilities/ostream.hpp"
  70 #if INCLUDE_TRACE
  71 #include "trace/tracing.hpp"
  72 #endif
  73 
  74 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
  75 
  76 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies) :
  77   _class_loader(h_class_loader()),
  78   _is_anonymous(is_anonymous),
  79   // An anonymous class loader data doesn't have anything to keep
  80   // it from being unloaded during parsing of the anonymous class.
  81   // The null-class-loader should always be kept alive.
  82   _keep_alive(is_anonymous || h_class_loader.is_null()),
  83   _metaspace(NULL), _unloading(false), _klasses(NULL),
  84   _claimed(0), _jmethod_ids(NULL), _handles(NULL), _deallocate_list(NULL),
  85   _next(NULL), _dependencies(dependencies),
  86   _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true,
  87                             Monitor::_safepoint_check_never)) {
  88     // empty
  89 }
  90 
  91 void ClassLoaderData::init_dependencies(TRAPS) {
  92   assert(!Universe::is_fully_initialized(), "should only be called when initializing");
  93   assert(is_the_null_class_loader_data(), "should only call this for the null class loader");
  94   _dependencies.init(CHECK);
  95 }
  96 
  97 void ClassLoaderData::Dependencies::init(TRAPS) {
  98   // Create empty dependencies array to add to. CMS requires this to be
  99   // an oop so that it can track additions via card marks.  We think.
 100   _list_head = oopFactory::new_objectArray(2, CHECK);
 101 }
 102 
 103 bool ClassLoaderData::claim() {
 104   if (_claimed == 1) {
 105     return false;
 106   }
 107 
 108   return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;
 109 }
 110 
 111 void ClassLoaderData::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 112   if (must_claim && !claim()) {
 113     return;
 114   }
 115 
 116   f->do_oop(&_class_loader);
 117   _dependencies.oops_do(f);
 118   _handles->oops_do(f);
 119   if (klass_closure != NULL) {
 120     classes_do(klass_closure);
 121   }
 122 }
 123 
 124 void ClassLoaderData::Dependencies::oops_do(OopClosure* f) {
 125   f->do_oop((oop*)&_list_head);
 126 }
 127 
 128 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
 129   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 130     klass_closure->do_klass(k);
 131     assert(k != k->next_link(), "no loops!");
 132   }
 133 }
 134 
 135 void ClassLoaderData::classes_do(void f(Klass * const)) {
 136   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 137     f(k);
 138   }
 139 }
 140 
 141 void ClassLoaderData::methods_do(void f(Method*)) {
 142   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 143     if (k->oop_is_instance()) {
 144       InstanceKlass::cast(k)->methods_do(f);
 145     }
 146   }
 147 }
 148 
 149 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
 150   // Lock to avoid classes being modified/added/removed during iteration
 151   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 152   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 153     // Do not filter ArrayKlass oops here...
 154     if (k->oop_is_array() || (k->oop_is_instance() && InstanceKlass::cast(k)->is_loaded())) {
 155       klass_closure->do_klass(k);
 156     }
 157   }
 158 }
 159 
 160 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
 161   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 162     if (k->oop_is_instance()) {
 163       f(InstanceKlass::cast(k));
 164     }
 165     assert(k != k->next_link(), "no loops!");
 166   }
 167 }
 168 
 169 void ClassLoaderData::record_dependency(Klass* k, TRAPS) {
 170   ClassLoaderData * const from_cld = this;
 171   ClassLoaderData * const to_cld = k->class_loader_data();
 172 
 173   // Dependency to the null class loader data doesn't need to be recorded
 174   // because the null class loader data never goes away.
 175   if (to_cld->is_the_null_class_loader_data()) {
 176     return;
 177   }
 178 
 179   oop to;
 180   if (to_cld->is_anonymous()) {
 181     // Anonymous class dependencies are through the mirror.
 182     to = k->java_mirror();
 183   } else {
 184     to = to_cld->class_loader();
 185 
 186     // If from_cld is anonymous, even if it's class_loader is a parent of 'to'
 187     // we still have to add it.  The class_loader won't keep from_cld alive.
 188     if (!from_cld->is_anonymous()) {
 189       // Check that this dependency isn't from the same or parent class_loader
 190       oop from = from_cld->class_loader();
 191 
 192       oop curr = from;
 193       while (curr != NULL) {
 194         if (curr == to) {
 195           return; // this class loader is in the parent list, no need to add it.
 196         }
 197         curr = java_lang_ClassLoader::parent(curr);
 198       }
 199     }
 200   }
 201 
 202   // It's a dependency we won't find through GC, add it. This is relatively rare
 203   // Must handle over GC point.
 204   Handle dependency(THREAD, to);
 205   from_cld->_dependencies.add(dependency, CHECK);
 206 }
 207 
 208 
 209 void ClassLoaderData::Dependencies::add(Handle dependency, TRAPS) {
 210   // Check first if this dependency is already in the list.
 211   // Save a pointer to the last to add to under the lock.
 212   objArrayOop ok = _list_head;
 213   objArrayOop last = NULL;
 214   while (ok != NULL) {
 215     last = ok;
 216     if (ok->obj_at(0) == dependency()) {
 217       // Don't need to add it
 218       return;
 219     }
 220     ok = (objArrayOop)ok->obj_at(1);
 221   }
 222 
 223   // Must handle over GC points
 224   assert (last != NULL, "dependencies should be initialized");
 225   objArrayHandle last_handle(THREAD, last);
 226 
 227   // Create a new dependency node with fields for (class_loader or mirror, next)
 228   objArrayOop deps = oopFactory::new_objectArray(2, CHECK);
 229   deps->obj_at_put(0, dependency());
 230 
 231   // Must handle over GC points
 232   objArrayHandle new_dependency(THREAD, deps);
 233 
 234   // Add the dependency under lock
 235   locked_add(last_handle, new_dependency, THREAD);
 236 }
 237 
 238 void ClassLoaderData::Dependencies::locked_add(objArrayHandle last_handle,
 239                                                objArrayHandle new_dependency,
 240                                                Thread* THREAD) {
 241 
 242   // Have to lock and put the new dependency on the end of the dependency
 243   // array so the card mark for CMS sees that this dependency is new.
 244   // Can probably do this lock free with some effort.
 245   ObjectLocker ol(Handle(THREAD, _list_head), THREAD);
 246 
 247   oop loader_or_mirror = new_dependency->obj_at(0);
 248 
 249   // Since the dependencies are only added, add to the end.
 250   objArrayOop end = last_handle();
 251   objArrayOop last = NULL;
 252   while (end != NULL) {
 253     last = end;
 254     // check again if another thread added it to the end.
 255     if (end->obj_at(0) == loader_or_mirror) {
 256       // Don't need to add it
 257       return;
 258     }
 259     end = (objArrayOop)end->obj_at(1);
 260   }
 261   assert (last != NULL, "dependencies should be initialized");
 262   // fill in the first element with the oop in new_dependency.
 263   if (last->obj_at(0) == NULL) {
 264     last->obj_at_put(0, new_dependency->obj_at(0));
 265   } else {
 266     last->obj_at_put(1, new_dependency());
 267   }
 268 }
 269 
 270 void ClassLoaderDataGraph::clear_claimed_marks() {
 271   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 272     cld->clear_claimed();
 273   }
 274 }
 275 
 276 void ClassLoaderData::add_class(Klass* k) {
 277   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 278   Klass* old_value = _klasses;
 279   k->set_next_link(old_value);
 280   // Make sure linked class is stable, since the class list is walked without a lock
 281   OrderAccess::storestore();
 282   // link the new item into the list
 283   _klasses = k;
 284 
 285   if (TraceClassLoaderData && Verbose && k->class_loader_data() != NULL) {
 286     ResourceMark rm;
 287     tty->print_cr("[TraceClassLoaderData] Adding k: " PTR_FORMAT " %s to CLD: "
 288                   PTR_FORMAT " loader: " PTR_FORMAT " %s",
 289                   p2i(k),
 290                   k->external_name(),
 291                   p2i(k->class_loader_data()),
 292                   p2i((void *)k->class_loader()),
 293                   loader_name());
 294   }
 295 }
 296 
 297 // This is called by InstanceKlass::deallocate_contents() to remove the
 298 // scratch_class for redefine classes.  We need a lock because there it may not
 299 // be called at a safepoint if there's an error.
 300 void ClassLoaderData::remove_class(Klass* scratch_class) {
 301   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 302   Klass* prev = NULL;
 303   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 304     if (k == scratch_class) {
 305       if (prev == NULL) {
 306         _klasses = k->next_link();
 307       } else {
 308         Klass* next = k->next_link();
 309         prev->set_next_link(next);
 310       }
 311       return;
 312     }
 313     prev = k;
 314     assert(k != k->next_link(), "no loops!");
 315   }
 316   ShouldNotReachHere();   // should have found this class!!
 317 }
 318 
 319 void ClassLoaderData::unload() {
 320   _unloading = true;
 321 
 322   // Tell serviceability tools these classes are unloading
 323   classes_do(InstanceKlass::notify_unload_class);
 324 
 325   if (TraceClassLoaderData) {
 326     ResourceMark rm;
 327     tty->print("[ClassLoaderData: unload loader data " INTPTR_FORMAT, p2i(this));
 328     tty->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)class_loader()),
 329                loader_name());
 330     if (is_anonymous()) {
 331       tty->print(" for anonymous class  " INTPTR_FORMAT " ", p2i(_klasses));
 332     }
 333     tty->print_cr("]");
 334   }
 335 }
 336 
 337 oop ClassLoaderData::keep_alive_object() const {
 338   assert(!keep_alive(), "Don't use with CLDs that are artificially kept alive");
 339   return is_anonymous() ? _klasses->java_mirror() : class_loader();
 340 }
 341 
 342 bool ClassLoaderData::is_alive(BoolObjectClosure* is_alive_closure) const {
 343   bool alive = keep_alive() // null class loader and incomplete anonymous klasses.
 344       || is_alive_closure->do_object_b(keep_alive_object());
 345 
 346   return alive;
 347 }
 348 
 349 
 350 ClassLoaderData::~ClassLoaderData() {
 351   // Release C heap structures for all the classes.
 352   classes_do(InstanceKlass::release_C_heap_structures);
 353 
 354   Metaspace *m = _metaspace;
 355   if (m != NULL) {
 356     _metaspace = NULL;
 357     // release the metaspace
 358     delete m;
 359     // release the handles
 360     if (_handles != NULL) {
 361       JNIHandleBlock::release_block(_handles);
 362       _handles = NULL;
 363     }
 364   }
 365 
 366   // Clear all the JNI handles for methods
 367   // These aren't deallocated and are going to look like a leak, but that's
 368   // needed because we can't really get rid of jmethodIDs because we don't
 369   // know when native code is going to stop using them.  The spec says that
 370   // they're "invalid" but existing programs likely rely on their being
 371   // NULL after class unloading.
 372   if (_jmethod_ids != NULL) {
 373     Method::clear_jmethod_ids(this);
 374   }
 375   // Delete lock
 376   delete _metaspace_lock;
 377 
 378   // Delete free list
 379   if (_deallocate_list != NULL) {
 380     delete _deallocate_list;
 381   }
 382 }
 383 
 384 /**
 385  * Returns true if this class loader data is for the extension class loader.
 386  */
 387 bool ClassLoaderData::is_ext_class_loader_data() const {
 388   return SystemDictionary::is_ext_class_loader(class_loader());
 389 }
 390 
 391 Metaspace* ClassLoaderData::metaspace_non_null() {
 392   assert(!DumpSharedSpaces, "wrong metaspace!");
 393   // If the metaspace has not been allocated, create a new one.  Might want
 394   // to create smaller arena for Reflection class loaders also.
 395   // The reason for the delayed allocation is because some class loaders are
 396   // simply for delegating with no metadata of their own.
 397   if (_metaspace == NULL) {
 398     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 399     // Check again if metaspace has been allocated while we were getting this lock.
 400     if (_metaspace != NULL) {
 401       return _metaspace;
 402     }
 403     if (this == the_null_class_loader_data()) {
 404       assert (class_loader() == NULL, "Must be");
 405       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType));
 406     } else if (is_anonymous()) {
 407       if (TraceClassLoaderData && Verbose && class_loader() != NULL) {
 408         tty->print_cr("is_anonymous: %s", class_loader()->klass()->internal_name());
 409       }
 410       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType));
 411     } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
 412       if (TraceClassLoaderData && Verbose && class_loader() != NULL) {
 413         tty->print_cr("is_reflection: %s", class_loader()->klass()->internal_name());
 414       }
 415       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType));
 416     } else {
 417       set_metaspace(new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType));
 418     }
 419   }
 420   return _metaspace;
 421 }
 422 
 423 JNIHandleBlock* ClassLoaderData::handles() const           { return _handles; }
 424 void ClassLoaderData::set_handles(JNIHandleBlock* handles) { _handles = handles; }
 425 
 426 jobject ClassLoaderData::add_handle(Handle h) {
 427   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 428   if (handles() == NULL) {
 429     set_handles(JNIHandleBlock::allocate_block());
 430   }
 431   return handles()->allocate_handle(h());
 432 }
 433 
 434 // Add this metadata pointer to be freed when it's safe.  This is only during
 435 // class unloading because Handles might point to this metadata field.
 436 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
 437   // Metadata in shared region isn't deleted.
 438   if (!m->is_shared()) {
 439     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 440     if (_deallocate_list == NULL) {
 441       _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, true);
 442     }
 443     _deallocate_list->append_if_missing(m);
 444   }
 445 }
 446 
 447 // Deallocate free metadata on the free list.  How useful the PermGen was!
 448 void ClassLoaderData::free_deallocate_list() {
 449   // Don't need lock, at safepoint
 450   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 451   if (_deallocate_list == NULL) {
 452     return;
 453   }
 454   // Go backwards because this removes entries that are freed.
 455   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 456     Metadata* m = _deallocate_list->at(i);
 457     if (!m->on_stack()) {
 458       _deallocate_list->remove_at(i);
 459       // There are only three types of metadata that we deallocate directly.
 460       // Cast them so they can be used by the template function.
 461       if (m->is_method()) {
 462         MetadataFactory::free_metadata(this, (Method*)m);
 463       } else if (m->is_constantPool()) {
 464         MetadataFactory::free_metadata(this, (ConstantPool*)m);
 465       } else if (m->is_klass()) {
 466         MetadataFactory::free_metadata(this, (InstanceKlass*)m);
 467       } else {
 468         ShouldNotReachHere();
 469       }
 470     }
 471   }
 472 }
 473 
 474 // These anonymous class loaders are to contain classes used for JSR292
 475 ClassLoaderData* ClassLoaderData::anonymous_class_loader_data(oop loader, TRAPS) {
 476   // Add a new class loader data to the graph.
 477   return ClassLoaderDataGraph::add(loader, true, THREAD);
 478 }
 479 
 480 const char* ClassLoaderData::loader_name() {
 481   // Handles null class loader
 482   return SystemDictionary::loader_name(class_loader());
 483 }
 484 
 485 #ifndef PRODUCT
 486 // Define to dump klasses
 487 #undef CLD_DUMP_KLASSES
 488 
 489 void ClassLoaderData::dump(outputStream * const out) {
 490   ResourceMark rm;
 491   out->print("ClassLoaderData CLD: "PTR_FORMAT", loader: "PTR_FORMAT", loader_klass: "PTR_FORMAT" %s {",
 492       p2i(this), p2i((void *)class_loader()),
 493       p2i(class_loader() != NULL ? class_loader()->klass() : NULL), loader_name());
 494   if (claimed()) out->print(" claimed ");
 495   if (is_unloading()) out->print(" unloading ");
 496   out->print(" handles " INTPTR_FORMAT, p2i(handles()));
 497   out->cr();
 498   if (metaspace_or_null() != NULL) {
 499     out->print_cr("metaspace: " INTPTR_FORMAT, p2i(metaspace_or_null()));
 500     metaspace_or_null()->dump(out);
 501   } else {
 502     out->print_cr("metaspace: NULL");
 503   }
 504 
 505 #ifdef CLD_DUMP_KLASSES
 506   if (Verbose) {
 507     ResourceMark rm;
 508     Klass* k = _klasses;
 509     while (k != NULL) {
 510       out->print_cr("klass "PTR_FORMAT", %s, CT: %d, MUT: %d", k, k->name()->as_C_string(),
 511           k->has_modified_oops(), k->has_accumulated_modified_oops());
 512       assert(k != k->next_link(), "no loops!");
 513       k = k->next_link();
 514     }
 515   }
 516 #endif  // CLD_DUMP_KLASSES
 517 #undef CLD_DUMP_KLASSES
 518   if (_jmethod_ids != NULL) {
 519     Method::print_jmethod_ids(this, out);
 520   }
 521   out->print_cr("}");
 522 }
 523 #endif // PRODUCT
 524 
 525 void ClassLoaderData::verify() {
 526   oop cl = class_loader();
 527 
 528   guarantee(this == class_loader_data(cl) || is_anonymous(), "Must be the same");
 529   guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || is_anonymous(), "must be");
 530 
 531   // Verify the integrity of the allocated space.
 532   if (metaspace_or_null() != NULL) {
 533     metaspace_or_null()->verify();
 534   }
 535 
 536   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 537     guarantee(k->class_loader_data() == this, "Must be the same");
 538     k->verify();
 539     assert(k != k->next_link(), "no loops!");
 540   }
 541 }
 542 
 543 bool ClassLoaderData::contains_klass(Klass* klass) {
 544   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 545     if (k == klass) return true;
 546   }
 547   return false;
 548 }
 549 
 550 
 551 // GC root of class loader data created.
 552 ClassLoaderData* ClassLoaderDataGraph::_head = NULL;
 553 ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
 554 ClassLoaderData* ClassLoaderDataGraph::_saved_unloading = NULL;
 555 ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
 556 
 557 bool ClassLoaderDataGraph::_should_purge = false;
 558 bool ClassLoaderDataGraph::_metaspace_oom = false;
 559 
 560 // Add a new class loader data node to the list.  Assign the newly created
 561 // ClassLoaderData into the java/lang/ClassLoader object as a hidden field
 562 ClassLoaderData* ClassLoaderDataGraph::add(Handle loader, bool is_anonymous, TRAPS) {
 563   // We need to allocate all the oops for the ClassLoaderData before allocating the
 564   // actual ClassLoaderData object.
 565   ClassLoaderData::Dependencies dependencies(CHECK_NULL);
 566 
 567   No_Safepoint_Verifier no_safepoints; // we mustn't GC until we've installed the
 568                                        // ClassLoaderData in the graph since the CLD
 569                                        // contains unhandled oops
 570 
 571   ClassLoaderData* cld = new ClassLoaderData(loader, is_anonymous, dependencies);
 572 
 573 
 574   if (!is_anonymous) {
 575     ClassLoaderData** cld_addr = java_lang_ClassLoader::loader_data_addr(loader());
 576     // First, Atomically set it
 577     ClassLoaderData* old = (ClassLoaderData*) Atomic::cmpxchg_ptr(cld, cld_addr, NULL);
 578     if (old != NULL) {
 579       delete cld;
 580       // Returns the data.
 581       return old;
 582     }
 583   }
 584 
 585   // We won the race, and therefore the task of adding the data to the list of
 586   // class loader data
 587   ClassLoaderData** list_head = &_head;
 588   ClassLoaderData* next = _head;
 589 
 590   do {
 591     cld->set_next(next);
 592     ClassLoaderData* exchanged = (ClassLoaderData*)Atomic::cmpxchg_ptr(cld, list_head, next);
 593     if (exchanged == next) {
 594       if (TraceClassLoaderData) {
 595         ResourceMark rm;
 596         tty->print("[ClassLoaderData: ");
 597         tty->print("create class loader data " INTPTR_FORMAT, p2i(cld));
 598         tty->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)cld->class_loader()),
 599                    cld->loader_name());
 600         tty->print_cr("]");
 601       }
 602       return cld;
 603     }
 604     next = exchanged;
 605   } while (true);
 606 
 607 }
 608 
 609 void ClassLoaderDataGraph::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 610   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 611     cld->oops_do(f, klass_closure, must_claim);
 612   }
 613 }
 614 
 615 void ClassLoaderDataGraph::keep_alive_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 616   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 617     if (cld->keep_alive()) {
 618       cld->oops_do(f, klass_closure, must_claim);
 619     }
 620   }
 621 }
 622 
 623 void ClassLoaderDataGraph::always_strong_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 624   if (ClassUnloading) {
 625     keep_alive_oops_do(f, klass_closure, must_claim);
 626   } else {
 627     oops_do(f, klass_closure, must_claim);
 628   }
 629 }
 630 
 631 void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {
 632   for (ClassLoaderData* cld = _head; cl != NULL && cld != NULL; cld = cld->next()) {
 633     cl->do_cld(cld);
 634   }
 635 }
 636 
 637 void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {
 638   for (ClassLoaderData* cld = _head;  cld != NULL; cld = cld->_next) {
 639     CLDClosure* closure = cld->keep_alive() ? strong : weak;
 640     if (closure != NULL) {
 641       closure->do_cld(cld);
 642     }
 643   }
 644 }
 645 
 646 void ClassLoaderDataGraph::keep_alive_cld_do(CLDClosure* cl) {
 647   roots_cld_do(cl, NULL);
 648 }
 649 
 650 void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
 651   if (ClassUnloading) {
 652     keep_alive_cld_do(cl);
 653   } else {
 654     cld_do(cl);
 655   }
 656 }
 657 
 658 void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
 659   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 660     cld->classes_do(klass_closure);
 661   }
 662 }
 663 
 664 void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
 665   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 666     cld->classes_do(f);
 667   }
 668 }
 669 
 670 void ClassLoaderDataGraph::methods_do(void f(Method*)) {
 671   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 672     cld->methods_do(f);
 673   }
 674 }
 675 
 676 void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
 677   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 678     cld->loaded_classes_do(klass_closure);
 679   }
 680 }
 681 
 682 void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
 683   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 684   // Only walk the head until any clds not purged from prior unloading
 685   // (CMS doesn't purge right away).
 686   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 687     cld->classes_do(f);
 688   }
 689 }
 690 
 691 GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
 692   assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
 693 
 694   GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
 695 
 696   // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
 697   ClassLoaderData* curr = _head;
 698   while (curr != _saved_head) {
 699     if (!curr->claimed()) {
 700       array->push(curr);
 701 
 702       if (TraceClassLoaderData) {
 703         tty->print("[ClassLoaderData] found new CLD: ");
 704         curr->print_value_on(tty);
 705         tty->cr();
 706       }
 707     }
 708 
 709     curr = curr->_next;
 710   }
 711 
 712   return array;
 713 }
 714 
 715 bool ClassLoaderDataGraph::unload_list_contains(const void* x) {
 716   assert(SafepointSynchronize::is_at_safepoint(), "only safe to call at safepoint");
 717   for (ClassLoaderData* cld = _unloading; cld != NULL; cld = cld->next()) {
 718     if (cld->metaspace_or_null() != NULL && cld->metaspace_or_null()->contains(x)) {
 719       return true;
 720     }
 721   }
 722   return false;
 723 }
 724 
 725 #ifndef PRODUCT
 726 bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
 727   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 728     if (loader_data == data) {
 729       return true;
 730     }
 731   }
 732 
 733   return false;
 734 }
 735 #endif // PRODUCT
 736 
 737 
 738 // Move class loader data from main list to the unloaded list for unloading
 739 // and deallocation later.
 740 bool ClassLoaderDataGraph::do_unloading(BoolObjectClosure* is_alive_closure, bool clean_alive) {
 741   ClassLoaderData* data = _head;
 742   ClassLoaderData* prev = NULL;
 743   bool seen_dead_loader = false;
 744 
 745   // Save previous _unloading pointer for CMS which may add to unloading list before
 746   // purging and we don't want to rewalk the previously unloaded class loader data.
 747   _saved_unloading = _unloading;
 748 
 749   data = _head;
 750   while (data != NULL) {
 751     if (data->is_alive(is_alive_closure)) {
 752       prev = data;
 753       data = data->next();
 754       continue;
 755     }
 756     seen_dead_loader = true;
 757     ClassLoaderData* dead = data;
 758     dead->unload();
 759     data = data->next();
 760     // Remove from loader list.
 761     // This class loader data will no longer be found
 762     // in the ClassLoaderDataGraph.
 763     if (prev != NULL) {
 764       prev->set_next(data);
 765     } else {
 766       assert(dead == _head, "sanity check");
 767       _head = data;
 768     }
 769     dead->set_next(_unloading);
 770     _unloading = dead;
 771   }
 772 
 773   if (clean_alive) {
 774     // Clean previous versions and the deallocate list.
 775     ClassLoaderDataGraph::clean_metaspaces();
 776   }
 777 
 778   if (seen_dead_loader) {
 779     post_class_unload_events();
 780   }
 781 
 782   return seen_dead_loader;
 783 }
 784 
 785 void ClassLoaderDataGraph::clean_metaspaces() {
 786   // mark metadata seen on the stack and code cache so we can delete unneeded entries.
 787   bool has_redefined_a_class = JvmtiExport::has_redefined_a_class();
 788   MetadataOnStackMark md_on_stack(has_redefined_a_class);
 789 
 790   if (has_redefined_a_class) {
 791     for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 792       data->classes_do(InstanceKlass::purge_previous_versions);
 793     }
 794   }
 795 
 796   // Should purge the previous version before deallocating.
 797   free_deallocate_lists();
 798 }
 799 
 800 void ClassLoaderDataGraph::purge() {
 801   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 802   ClassLoaderData* list = _unloading;
 803   _unloading = NULL;
 804   ClassLoaderData* next = list;
 805   bool classes_unloaded = false;
 806   while (next != NULL) {
 807     ClassLoaderData* purge_me = next;
 808     next = purge_me->next();
 809     delete purge_me;
 810     classes_unloaded = true;
 811   }
 812   if (classes_unloaded) {
 813     Metaspace::purge();
 814     set_metaspace_oom(false);
 815   }
 816 }
 817 
 818 void ClassLoaderDataGraph::post_class_unload_events(void) {
 819 #if INCLUDE_TRACE
 820   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 821   if (Tracing::enabled()) {
 822     if (Tracing::is_event_enabled(TraceClassUnloadEvent)) {
 823       assert(_unloading != NULL, "need class loader data unload list!");
 824       _class_unload_time = Ticks::now();
 825       classes_unloading_do(&class_unload_event);
 826     }
 827     Tracing::on_unloading_classes();
 828   }
 829 #endif
 830 }
 831 
 832 void ClassLoaderDataGraph::free_deallocate_lists() {
 833   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 834     cld->free_deallocate_list();
 835   }
 836 }
 837 
 838 // CDS support
 839 
 840 // Global metaspaces for writing information to the shared archive.  When
 841 // application CDS is supported, we may need one per metaspace, so this
 842 // sort of looks like it.
 843 Metaspace* ClassLoaderData::_ro_metaspace = NULL;
 844 Metaspace* ClassLoaderData::_rw_metaspace = NULL;
 845 static bool _shared_metaspaces_initialized = false;
 846 
 847 // Initialize shared metaspaces (change to call from somewhere not lazily)
 848 void ClassLoaderData::initialize_shared_metaspaces() {
 849   assert(DumpSharedSpaces, "only use this for dumping shared spaces");
 850   assert(this == ClassLoaderData::the_null_class_loader_data(),
 851          "only supported for null loader data for now");
 852   assert (!_shared_metaspaces_initialized, "only initialize once");
 853   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 854   _ro_metaspace = new Metaspace(_metaspace_lock, Metaspace::ROMetaspaceType);
 855   _rw_metaspace = new Metaspace(_metaspace_lock, Metaspace::ReadWriteMetaspaceType);
 856   _shared_metaspaces_initialized = true;
 857 }
 858 
 859 Metaspace* ClassLoaderData::ro_metaspace() {
 860   assert(_ro_metaspace != NULL, "should already be initialized");
 861   return _ro_metaspace;
 862 }
 863 
 864 Metaspace* ClassLoaderData::rw_metaspace() {
 865   assert(_rw_metaspace != NULL, "should already be initialized");
 866   return _rw_metaspace;
 867 }
 868 
 869 ClassLoaderDataGraphKlassIteratorAtomic::ClassLoaderDataGraphKlassIteratorAtomic()
 870     : _next_klass(NULL) {
 871   ClassLoaderData* cld = ClassLoaderDataGraph::_head;
 872   Klass* klass = NULL;
 873 
 874   // Find the first klass in the CLDG.
 875   while (cld != NULL) {
 876     klass = cld->_klasses;
 877     if (klass != NULL) {
 878       _next_klass = klass;
 879       return;
 880     }
 881     cld = cld->next();
 882   }
 883 }
 884 
 885 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass_in_cldg(Klass* klass) {
 886   Klass* next = klass->next_link();
 887   if (next != NULL) {
 888     return next;
 889   }
 890 
 891   // No more klasses in the current CLD. Time to find a new CLD.
 892   ClassLoaderData* cld = klass->class_loader_data();
 893   while (next == NULL) {
 894     cld = cld->next();
 895     if (cld == NULL) {
 896       break;
 897     }
 898     next = cld->_klasses;
 899   }
 900 
 901   return next;
 902 }
 903 
 904 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass() {
 905   Klass* head = _next_klass;
 906 
 907   while (head != NULL) {
 908     Klass* next = next_klass_in_cldg(head);
 909 
 910     Klass* old_head = (Klass*)Atomic::cmpxchg_ptr(next, &_next_klass, head);
 911 
 912     if (old_head == head) {
 913       return head; // Won the CAS.
 914     }
 915 
 916     head = old_head;
 917   }
 918 
 919   // Nothing more for the iterator to hand out.
 920   assert(head == NULL, err_msg("head is " PTR_FORMAT ", expected not null:", p2i(head)));
 921   return NULL;
 922 }
 923 
 924 ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
 925   _data = ClassLoaderDataGraph::_head;
 926 }
 927 
 928 ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
 929 
 930 #ifndef PRODUCT
 931 // callable from debugger
 932 extern "C" int print_loader_data_graph() {
 933   ClassLoaderDataGraph::dump_on(tty);
 934   return 0;
 935 }
 936 
 937 void ClassLoaderDataGraph::verify() {
 938   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 939     data->verify();
 940   }
 941 }
 942 
 943 void ClassLoaderDataGraph::dump_on(outputStream * const out) {
 944   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 945     data->dump(out);
 946   }
 947   MetaspaceAux::dump(out);
 948 }
 949 #endif // PRODUCT
 950 
 951 void ClassLoaderData::print_value_on(outputStream* out) const {
 952   if (class_loader() == NULL) {
 953     out->print("NULL class_loader");
 954   } else {
 955     out->print("class loader " INTPTR_FORMAT, p2i(this));
 956     class_loader()->print_value_on(out);
 957   }
 958 }
 959 
 960 #if INCLUDE_TRACE
 961 
 962 Ticks ClassLoaderDataGraph::_class_unload_time;
 963 
 964 void ClassLoaderDataGraph::class_unload_event(Klass* const k) {
 965 
 966   // post class unload event
 967   EventClassUnload event(UNTIMED);
 968   event.set_endtime(_class_unload_time);
 969   event.set_unloadedClass(k);
 970   oop defining_class_loader = k->class_loader();
 971   event.set_definingClassLoader(defining_class_loader != NULL ?
 972                                 defining_class_loader->klass() : (Klass*)NULL);
 973   event.commit();
 974 }
 975 
 976 #endif // INCLUDE_TRACE
--- EOF ---