/*

 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

// A ClassLoaderData identifies the full set of class types that a class

// loader's name resolution strategy produces for a given configuration of the

// class loader.

// Class types in the ClassLoaderData may be defined by from class file binaries

// provided by the class loader, or from other class loader it interacts with

// according to its name resolution strategy.

//

// Class loaders that implement a deterministic name resolution strategy

// (including with respect to their delegation behavior), such as the boot, the

// extension, and the system loaders of the JDK's built-in class loader

// hierarchy, always produce the same linkset for a given configuration.

//

// ClassLoaderData carries information related to a linkset (e.g.,

// metaspace holding its klass definitions).

// The System Dictionary and related data structures (e.g., placeholder table,

// loader constraints table) as well as the runtime representation of classes

// only reference ClassLoaderData.

//

// Instances of java.lang.ClassLoader holds a pointer to a ClassLoaderData that

// that represent the loader's "linking domain" in the JVM.

//

// The bootstrap loader (represented by NULL) also has a ClassLoaderData,

// the singleton class the_null_class_loader_data().

#include "precompiled.hpp"

#include "classfile/classLoaderData.hpp"

#include "classfile/classLoaderData.inline.hpp"

#include "classfile/javaClasses.hpp"

#include "classfile/systemDictionary.hpp"

#include "code/codeCache.hpp"

#include "memory/metadataFactory.hpp"

#include "memory/metaspaceShared.hpp"

#include "prims/jvmtiRedefineClasses.hpp"

#include "runtime/jniHandles.hpp"

#include "runtime/mutex.hpp"

#include "runtime/safepoint.hpp"

#include "runtime/synchronizer.hpp"

#include "utilities/growableArray.hpp"

#include "utilities/ostream.hpp"

ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;

ClassLoaderData::ClassLoaderData(Handle h_class_loader) : _class_loader(h_class_loader()),

  _metaspace(NULL), _unloading(false), _klasses(NULL),

  _claimed(0), _jmethod_ids(NULL), _handles(NULL),

  _deallocate_list(NULL), _next(NULL),

  _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true)) {

    // empty

}

bool ClassLoaderData::claim() {

  if (_claimed == 1) {

    return false;

  }

  return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;

}

void ClassLoaderData::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {

  if (must_claim && !claim()) {

    return;

  }

  f->do_oop(&_class_loader);

  _handles->oops_do(f);

  if (klass_closure != NULL) {

    classes_do(klass_closure);

  }

}

void ClassLoaderData::classes_do(KlassClosure* klass_closure) {

  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {

    klass_closure->do_klass(k);

  }

}

void ClassLoaderData::classes_do(void f(InstanceKlass*)) {

  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {

    if (k->oop_is_instance()) {

      f(InstanceKlass::cast(k));

    }

  }

}

void ClassLoaderData::record_dependency(Klass* k, TRAPS) {

  ClassLoaderData * const from_cld = this;

  ClassLoaderData * const to_cld = k->class_loader_data();

  // Records dependency between non-null class loaders only.

  if (to_cld->is_the_null_class_loader_data() || from_cld->is_the_null_class_loader_data()) {

    return;

  }

  // Check that this dependency isn't from the same or parent class_loader

  oop to = to_cld->class_loader();

  oop from = from_cld->class_loader();

  oop curr = from;

  while (curr != NULL) {

    if (curr == to) {

      return; // this class loader is in the parent list, no need to add it.

    }

    curr = java_lang_ClassLoader::parent(curr);

  }

  // It's a dependency we won't find through GC, add it. This is relatively rare

  from_cld->add_dependency(to_cld, CHECK);

}

bool ClassLoaderData::has_dependency(ClassLoaderData* dependency) {

  oop loader = dependency->class_loader();

  // Get objArrayOop out of the class_loader oop and see if this dependency

  // is there.  Don't safepoint!  These are all oops.

  // Dependency list is (oop class_loader, objArrayOop next)

  objArrayOop ok = (objArrayOop)java_lang_ClassLoader::dependencies(class_loader());

  while (ok != NULL) {

    if (ok->obj_at(0) == loader) {

      return true;

    }

    ok = (objArrayOop)ok->obj_at(1);

  }

  return false;

}

void ClassLoaderData::add_dependency(ClassLoaderData* dependency, TRAPS) {

  // Minimize the number of duplicates in the list.

  if (has_dependency(dependency)) {

    return;

  }

  // Create a new dependency node with fields for (class_loader, next)

  objArrayOop deps = oopFactory::new_objectArray(2, CHECK);

  deps->obj_at_put(0, dependency->class_loader());

  // Add this lock free, using compare and exchange, need barriers for GC

  // Do the barrier first.

  HeapWord* addr = java_lang_ClassLoader::dependencies_addr(class_loader());

  while (true) {

    oop old_dependency = java_lang_ClassLoader::dependencies(class_loader());

    deps->obj_at_put(1, old_dependency);

    oop newold = oopDesc::atomic_compare_exchange_oop((oop)deps, addr, old_dependency, true);

    if (newold == old_dependency) {

      update_barrier_set((void*)addr, (oop)deps);

      // we won the race to add this dependency

      break;

    }

  }

}

void ClassLoaderDataGraph::clear_claimed_marks() {

  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {

    cld->clear_claimed();

  }

}

void ClassLoaderData::add_class(Klass* k) {

  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);

  Klass* old_value = _klasses;

  k->set_next_link(old_value);

  // link the new item into the list

  _klasses = k;

  if (TraceClassLoaderData && k->class_loader_data() != NULL) {

    ResourceMark rm;

    tty->print_cr("[TraceClassLoaderData] Adding k: " PTR_FORMAT " %s to CLD: "

                  PTR_FORMAT " loader: " PTR_FORMAT " %s",

                  k,

                  k->external_name(),

                  k->class_loader_data(),

                  k->class_loader(),

                  k->class_loader() != NULL ? k->class_loader()->klass()->external_name() : "NULL"

      );

  }

}

// This is called by InstanceKlass::deallocate_contents() to remove the

// scratch_class for redefine classes.  We need a lock because there it may not

// be called at a safepoint if there's an error.

void ClassLoaderData::remove_class(Klass* scratch_class) {

  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);

  Klass* prev = NULL;

  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {

    if (k == scratch_class) {

      if (prev == NULL) {

        _klasses = k->next_link();

      } else {

        Klass* next = k->next_link();

        prev->set_next_link(next);

      }

      return;

    }

    prev = k;

  }

  ShouldNotReachHere();   // should have found this class!!

}

ClassLoaderData::~ClassLoaderData() {

  Metaspace *m = _metaspace;

  if (m != NULL) {

    _metaspace = NULL;

    // release the metaspace

    delete m;

    // release the handles

    if (_handles != NULL) {

      JNIHandleBlock::release_block(_handles);

      _handles = NULL;

    }

  }

  // Clear all the JNI handles for methods

  // These aren't deallocated and are going to look like a leak, but that's

  // needed because we can't really get rid of jmethodIDs because we don't

  // know when native code is going to stop using them.  The spec says that

  // they're "invalid" but existing programs likely rely on their being

  // NULL after class unloading.

  if (_jmethod_ids != NULL) {

    Method::clear_jmethod_ids(this);

  }

  // Delete lock

  delete _metaspace_lock;

  // Delete free list

  if (_deallocate_list != NULL) {

    delete _deallocate_list;

  }

}

Metaspace* ClassLoaderData::metaspace_non_null() {

  // If the metaspace has not been allocated, create a new one.  Might want

  // to create smaller arena for Reflection class loaders also.

  // The reason for the delayed allocation is because some class loaders are

  // simply for delegating with no metadata of their own.

  if (_metaspace == NULL) {

    MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);

    // Check again if metaspace has been allocated while we were getting this lock.

    if (_metaspace != NULL) {

      return _metaspace;

    }

    if (class_loader() == NULL) {

      assert(this == the_null_class_loader_data(), "Must be");

      size_t word_size = Metaspace::first_chunk_word_size();

      set_metaspace(new Metaspace(_metaspace_lock, word_size));

    } else {

      set_metaspace(new Metaspace(_metaspace_lock));  // default size for now.

    }

  }

  return _metaspace;

}

JNIHandleBlock* ClassLoaderData::handles() const           { return _handles; }

void ClassLoaderData::set_handles(JNIHandleBlock* handles) { _handles = handles; }

jobject ClassLoaderData::add_handle(Handle h) {

  MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);

  if (handles() == NULL) {

    set_handles(JNIHandleBlock::allocate_block());

  }

  return handles()->allocate_handle(h());

}

// Add this metadata pointer to be freed when it's safe.  This is only during

// class unloading because Handles might point to this metadata field.

void ClassLoaderData::add_to_deallocate_list(Metadata* m) {

  // Metadata in shared region isn't deleted.

  if (!m->is_shared()) {

    MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);

    if (_deallocate_list == NULL) {

      _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, true);

    }

    _deallocate_list->append_if_missing(m);

  }

}

// Deallocate free metadata on the free list.  How useful the PermGen was!

void ClassLoaderData::free_deallocate_list() {

  // Don't need lock, at safepoint

  assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");

  if (_deallocate_list == NULL) {

    return;

  }

  // Go backwards because this removes entries that are freed.

  for (int i = _deallocate_list->length() - 1; i >= 0; i--) {

    Metadata* m = _deallocate_list->at(i);

    if (!m->on_stack()) {

      _deallocate_list->remove_at(i);

      // There are only three types of metadata that we deallocate directly.

      // Cast them so they can be used by the template function.

      if (m->is_method()) {

        MetadataFactory::free_metadata(this, (Method*)m);

      } else if (m->is_constantPool()) {

        MetadataFactory::free_metadata(this, (ConstantPool*)m);

      } else if (m->is_klass()) {

        MetadataFactory::free_metadata(this, (InstanceKlass*)m);

      } else {

        ShouldNotReachHere();

      }

    }

  }

}

#ifndef PRODUCT

void ClassLoaderData::print_loader(ClassLoaderData *loader_data, outputStream* out) {

  oop class_loader = loader_data->class_loader();

  out->print("%s", SystemDictionary::loader_name(class_loader));

}

// Define to dump klasses

#undef CLD_DUMP_KLASSES

void ClassLoaderData::dump(outputStream * const out) {

  ResourceMark rm;

  out->print("ClassLoaderData CLD: "PTR_FORMAT", loader: "PTR_FORMAT", loader_klass: "PTR_FORMAT" %s {",

      this, class_loader(),

      class_loader() != NULL ? class_loader()->klass() : NULL,

      class_loader() != NULL ? class_loader()->klass()->external_name() : "NULL");

  if (claimed()) out->print(" claimed ");

  if (is_unloading()) out->print(" unloading ");

  out->print(" handles " INTPTR_FORMAT, handles());

  out->cr();

  if (metaspace_or_null() != NULL) {

    out->print_cr("metaspace: " PTR_FORMAT, metaspace_or_null());

    metaspace_or_null()->dump(out);

  } else {

    out->print_cr("metaspace: NULL");

  }

#ifdef CLD_DUMP_KLASSES

  if (Verbose) {

    ResourceMark rm;

    Klass* k = _klasses;

    while (k != NULL) {

      out->print_cr("klass "PTR_FORMAT", %s, CT: %d, MUT: %d", k, k->name()->as_C_string(),

          k->has_modified_oops(), k->has_accumulated_modified_oops());

      k = k->next_link();

    }

  }

#endif  // CLD_DUMP_KLASSES

#undef CLD_DUMP_KLASSES

  if (_jmethod_ids != NULL) {

    Method::print_jmethod_ids(this, out);

  }

  out->print_cr("}");

}

#endif // PRODUCT

void ClassLoaderData::verify() {

  oop cl = class_loader();

  guarantee(this == class_loader_data(cl), "Must be the same");

  guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data(), "must be");

  // Verify the integrity of the allocated space.

  if (metaspace_or_null() != NULL) {

    metaspace_or_null()->verify();

  }

  for (Klass* k = _klasses; k != NULL; k = k->next_link()) {

    guarantee(k->class_loader_data() == this, "Must be the same");

    k->verify();

  }

}

// GC root of class loader data created.

ClassLoaderData* ClassLoaderDataGraph::_head = NULL;

ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;

ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;

// Add a new class loader data node to the list.  Assign the newly created

// ClassLoaderData into the java/lang/ClassLoader object as a hidden field

ClassLoaderData* ClassLoaderDataGraph::add(ClassLoaderData** cld_addr, Handle loader_data) {

  // Not assigned a class loader data yet.

  // Create one.

  ClassLoaderData* *list_head = &_head;

  ClassLoaderData* next = _head;

  ClassLoaderData* cld = new ClassLoaderData(loader_data);

  // First, Atomically set it.

  ClassLoaderData* old = (ClassLoaderData*) Atomic::cmpxchg_ptr(cld, cld_addr, NULL);

  if (old != NULL) {

    delete cld;

    // Returns the data.

    return old;

  }

  // We won the race, and therefore the task of adding the data to the list of

  // class loader data

  do {

    cld->set_next(next);

    ClassLoaderData* exchanged = (ClassLoaderData*)Atomic::cmpxchg_ptr(cld, list_head, next);

    if (exchanged == next) {

      if (TraceClassLoaderData) {

        tty->print("[ClassLoaderData: ");

        tty->print("create class loader data "PTR_FORMAT, cld);

        tty->print(" for instance "PTR_FORMAT" of ", cld->class_loader());

        loader_data->klass()->name()->print_symbol_on(tty);

        tty->print_cr("]");

      }

      return cld;

    }

    next = exchanged;

  } while (true);

}

void ClassLoaderDataGraph::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {

  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {

    cld->oops_do(f, klass_closure, must_claim);

  }

}

void ClassLoaderDataGraph::always_strong_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {

  if (ClassUnloading) {

    ClassLoaderData::the_null_class_loader_data()->oops_do(f, klass_closure, must_claim);

  } else {

    ClassLoaderDataGraph::oops_do(f, klass_closure, must_claim);

  }

}

void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {

  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {

    cld->classes_do(klass_closure);

  }

}

GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {

  assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");

  GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();

  // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);

  ClassLoaderData* curr = _head;

  while (curr != _saved_head) {

    if (!curr->claimed()) {

      array->push(curr);

      if (TraceClassLoaderData) {

        tty->print("[ClassLoaderData] found new CLD: ");

        curr->print_value_on(tty);

        tty->cr();

      }

    }

    curr = curr->_next;

  }

  return array;

}

#ifndef PRODUCT

// for debugging and hsfind(x)

bool ClassLoaderDataGraph::contains(address x) {

  // I think we need the _metaspace_lock taken here because the class loader

  // data graph could be changing while we are walking it (new entries added,

  // new entries being unloaded, etc).

  if (DumpSharedSpaces) {

    // There are only two metaspaces to worry about.

    ClassLoaderData* ncld = ClassLoaderData::the_null_class_loader_data();

    return (ncld->ro_metaspace()->contains(x) || ncld->rw_metaspace()->contains(x));

  }

  if (UseSharedSpaces && MetaspaceShared::is_in_shared_space(x)) {

    return true;

  }

  for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {

    if (cld->metaspace_or_null() != NULL && cld->metaspace_or_null()->contains(x)) {

      return true;

    }

  }

  // Could also be on an unloading list which is okay, ie. still allocated

  // for a little while.

  for (ClassLoaderData* ucld = _unloading; ucld != NULL; ucld = ucld->next()) {

    if (ucld->metaspace_or_null() != NULL && ucld->metaspace_or_null()->contains(x)) {

      return true;

    }

  }

  return false;

}

bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {

  for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {

    if (loader_data == data) {

      return true;

    }

  }

  return false;

}

#endif // PRODUCT

// Move class loader data from main list to the unloaded list for unloading

// and deallocation later.

bool ClassLoaderDataGraph::do_unloading(BoolObjectClosure* is_alive) {

  ClassLoaderData* data = _head;

  ClassLoaderData* prev = NULL;

  bool seen_dead_loader = false;

  // mark metadata seen on the stack and code cache so we can delete

  // unneeded entries.

  bool has_redefined_a_class = JvmtiExport::has_redefined_a_class();

  MetadataOnStackMark md_on_stack;

  while (data != NULL) {