/*

 * Copyright (c) 2012, 2018, 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.

 *

 */

#ifndef SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP

#define SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP

#include "memory/allocation.hpp"

#include "memory/memRegion.hpp"

#include "memory/metaspace.hpp"

#include "memory/metaspaceCounters.hpp"

#include "oops/oopHandle.hpp"

#include "runtime/mutex.hpp"

#include "trace/traceMacros.hpp"

#include "utilities/growableArray.hpp"

#include "utilities/macros.hpp"

#if INCLUDE_TRACE

#include "utilities/ticks.hpp"

#endif

//

// A class loader represents a linkset. Conceptually, a linkset identifies

// the complete transitive closure of resolved links that a dynamic linker can

// produce.

//

// A ClassLoaderData also encapsulates the allocation space, called a metaspace,

// used by the dynamic linker to allocate the runtime representation of all

// the types it defines.

//

// ClassLoaderData are stored in the runtime representation of classes,

// and provides iterators for root tracing and other GC operations.

class ClassLoaderData;

class JNIMethodBlock;

class Metadebug;

class ModuleEntry;

class PackageEntry;

class ModuleEntryTable;

class PackageEntryTable;

class DictionaryEntry;

class Dictionary;

// GC root for walking class loader data created

class ClassLoaderDataGraph : public AllStatic {

  friend class ClassLoaderData;

  friend class ClassLoaderDataGraphMetaspaceIterator;

  friend class ClassLoaderDataGraphKlassIteratorAtomic;

  friend class ClassLoaderDataGraphKlassIteratorStatic;

  friend class VMStructs;

 private:

  // All CLDs (except the null CLD) can be reached by walking _head->_next->...

  static ClassLoaderData* _head;

  static ClassLoaderData* _unloading;

  // CMS support.

  static ClassLoaderData* _saved_head;

  static ClassLoaderData* _saved_unloading;

  static bool _should_purge;

  // OOM has been seen in metaspace allocation. Used to prevent some

  // allocations until class unloading

  static bool _metaspace_oom;

  static volatile size_t  _num_instance_classes;

  static volatile size_t  _num_array_classes;

  static ClassLoaderData* add(Handle class_loader, bool anonymous);

  static void post_class_unload_events();

 public:

  static ClassLoaderData* find_or_create(Handle class_loader);

  static void purge();

  static void clear_claimed_marks();

  // oops do

  static void oops_do(OopClosure* f, bool must_claim);

  static void keep_alive_oops_do(OopClosure* blk, bool must_claim);

  static void always_strong_oops_do(OopClosure* blk, bool must_claim);

  // cld do

  static void cld_do(CLDClosure* cl);

  static void cld_unloading_do(CLDClosure* cl);

  static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);

  static void keep_alive_cld_do(CLDClosure* cl);

  static void always_strong_cld_do(CLDClosure* cl);

  // klass do

  // Walking classes through the ClassLoaderDataGraph include array classes.  It also includes

  // classes that are allocated but not loaded, classes that have errors, and scratch classes

  // for redefinition.  These classes are removed during the next class unloading.

  // Walking the ClassLoaderDataGraph also includes anonymous classes.

  static void classes_do(KlassClosure* klass_closure);

  static void classes_do(void f(Klass* const));

  static void methods_do(void f(Method*));

  static void modules_do(void f(ModuleEntry*));

  static void modules_unloading_do(void f(ModuleEntry*));

  static void packages_do(void f(PackageEntry*));

  static void packages_unloading_do(void f(PackageEntry*));

  static void loaded_classes_do(KlassClosure* klass_closure);

  static void classes_unloading_do(void f(Klass* const));

  static bool do_unloading(BoolObjectClosure* is_alive, bool clean_previous_versions);

  // dictionary do

  // Iterate over all klasses in dictionary, but

  // just the classes from defining class loaders.

  static void dictionary_classes_do(void f(InstanceKlass*));

  // Added for initialize_itable_for_klass to handle exceptions.

  static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS);

  // Iterate all classes and their class loaders, including initiating class loaders.

  static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*));

  // VM_CounterDecay iteration support

  static InstanceKlass* try_get_next_class();

  static void verify_dictionary();

  static void print_dictionary(outputStream* st);

  static void print_dictionary_statistics(outputStream* st);

  // CMS support.

  static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }

  static GrowableArray<ClassLoaderData*>* new_clds();

  static void set_should_purge(bool b) { _should_purge = b; }

  static void purge_if_needed() {

    // Only purge the CLDG for CMS if concurrent sweep is complete.

    if (_should_purge) {

      purge();

      // reset for next time.

      set_should_purge(false);

    }

  }

  static int resize_if_needed();

  static bool has_metaspace_oom()           { return _metaspace_oom; }

  static void set_metaspace_oom(bool value) { _metaspace_oom = value; }

  static void print_on(outputStream * const out) PRODUCT_RETURN;

  static void print() { print_on(tty); }

  static void verify();

  static bool unload_list_contains(const void* x);

  // instance and array class counters

  static inline size_t num_instance_classes();

  static inline size_t num_array_classes();

  static inline void inc_instance_classes(size_t count);

  static inline void dec_instance_classes(size_t count);

  static inline void inc_array_classes(size_t count);

  static inline void dec_array_classes(size_t count);

#ifndef PRODUCT

  static bool contains_loader_data(ClassLoaderData* loader_data);

#endif

#if INCLUDE_TRACE

 private:

  static Ticks _class_unload_time;

  static void class_unload_event(Klass* const k);

#endif

};

// ClassLoaderData class

class ClassLoaderData : public CHeapObj<mtClass> {

  friend class VMStructs;

 private:

  class ChunkedHandleList VALUE_OBJ_CLASS_SPEC {

    struct Chunk : public CHeapObj<mtClass> {

      static const size_t CAPACITY = 32;

      oop _data[CAPACITY];

      volatile juint _size;

      Chunk* _next;

      Chunk(Chunk* c) : _next(c), _size(0) { }

    };

    Chunk* volatile _head;

    void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);

   public:

    ChunkedHandleList() : _head(NULL) {}

    ~ChunkedHandleList();

    // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().

    // However, multiple threads can execute oops_do concurrently with add.

    oop* add(oop o);

    bool contains(oop p);

    void oops_do(OopClosure* f);

    int count() const;

  };

  friend class ClassLoaderDataGraph;

  friend class ClassLoaderDataGraphKlassIteratorAtomic;

  friend class ClassLoaderDataGraphKlassIteratorStatic;

  friend class ClassLoaderDataGraphMetaspaceIterator;

  friend class InstanceKlass;

  friend class MetaDataFactory;

  friend class Method;

  static ClassLoaderData * _the_null_class_loader_data;

  oop _class_loader;          // oop used to uniquely identify a class loader

                              // class loader or a canonical class path

  Metaspace * volatile _metaspace;  // Meta-space where meta-data defined by the

                                    // classes in the class loader are allocated.

  Mutex* _metaspace_lock;  // Locks the metaspace for allocations and setup.

  bool _unloading;         // true if this class loader goes away

  bool _is_anonymous;      // if this CLD is for an anonymous class

  // Remembered sets support for the oops in the class loader data.

  bool _modified_oops;             // Card Table Equivalent (YC/CMS support)

  bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)

  s2 _keep_alive;          // if this CLD is kept alive without a keep_alive_object().

                           // Used for anonymous classes and the boot class

                           // loader. _keep_alive does not need to be volatile or

                           // atomic since there is one unique CLD per anonymous class.

  volatile int _claimed;   // true if claimed, for example during GC traces.

                           // To avoid applying oop closure more than once.

                           // Has to be an int because we cas it.

  ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which

                              // have the same life cycle of the corresponding ClassLoader.

  NOT_PRODUCT(volatile int _dependency_count;)  // number of class loader dependencies

  Klass* volatile _klasses;              // The classes defined by the class loader.

  PackageEntryTable* volatile _packages; // The packages defined by the class loader.

  ModuleEntryTable*  volatile _modules;  // The modules defined by the class loader.

  ModuleEntry* _unnamed_module;          // This class loader's unnamed module.

  Dictionary*  _dictionary;              // The loaded InstanceKlasses, including initiated by this class loader

  // These method IDs are created for the class loader and set to NULL when the

  // class loader is unloaded.  They are rarely freed, only for redefine classes

  // and if they lose a data race in InstanceKlass.

  JNIMethodBlock*                  _jmethod_ids;

  // Metadata to be deallocated when it's safe at class unloading, when

  // this class loader isn't unloaded itself.

  GrowableArray<Metadata*>*      _deallocate_list;

  // Support for walking class loader data objects

  ClassLoaderData* _next; /// Next loader_datas created

  // ReadOnly and ReadWrite metaspaces (static because only on the null

  // class loader for now).

  static Metaspace* _ro_metaspace;

  static Metaspace* _rw_metaspace;

  TRACE_DEFINE_TRACE_ID_FIELD;

  void set_next(ClassLoaderData* next) { _next = next; }

  ClassLoaderData* next() const        { return _next; }

  ClassLoaderData(Handle h_class_loader, bool is_anonymous);

  ~ClassLoaderData();

  // The CLD are not placed in the Heap, so the Card Table or

  // the Mod Union Table can't be used to mark when CLD have modified oops.

  // The CT and MUT bits saves this information for the whole class loader data.

  void clear_modified_oops()             { _modified_oops = false; }

 public:

  void record_modified_oops()            { _modified_oops = true; }

  bool has_modified_oops()               { return _modified_oops; }

  void accumulate_modified_oops()        { if (has_modified_oops()) _accumulated_modified_oops = true; }

  void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }

  bool has_accumulated_modified_oops()   { return _accumulated_modified_oops; }

 private:

  void unload();

  bool keep_alive() const       { return _keep_alive > 0; }

  void classes_do(void f(Klass*));

  void loaded_classes_do(KlassClosure* klass_closure);

  void classes_do(void f(InstanceKlass*));

  void methods_do(void f(Method*));

  void modules_do(void f(ModuleEntry*));

  void packages_do(void f(PackageEntry*));

  // Deallocate free list during class unloading.

  void free_deallocate_list();      // for the classes that are not unloaded

  void unload_deallocate_list();    // for the classes that are unloaded

  // Allocate out of this class loader data

  MetaWord* allocate(size_t size);

  Dictionary* create_dictionary();

 public:

  // GC interface.

  void clear_claimed() { _claimed = 0; }

  bool claimed() const { return _claimed == 1; }

  bool claim();

  bool is_alive(BoolObjectClosure* is_alive_closure) const;

  // Accessors

  Metaspace* metaspace_or_null() const     { return _metaspace; }

  static ClassLoaderData* the_null_class_loader_data() {

    return _the_null_class_loader_data;

  }

  Mutex* metaspace_lock() const { return _metaspace_lock; }

  bool is_anonymous() const { return _is_anonymous; }

  static void init_null_class_loader_data();

  bool is_the_null_class_loader_data() const {

    return this == _the_null_class_loader_data;

  }

  bool is_system_class_loader_data() const;

  bool is_platform_class_loader_data() const;

  // Returns true if this class loader data is for the boot class loader.

  // (Note that the class loader data may be anonymous.)

  bool is_boot_class_loader_data() const {

    return class_loader() == NULL;

  }

  bool is_builtin_class_loader_data() const;

  bool is_permanent_class_loader_data() const;

  // The Metaspace is created lazily so may be NULL.  This

  // method will allocate a Metaspace if needed.

  Metaspace* metaspace_non_null();

  oop class_loader() const      { return _class_loader; }

  // The object the GC is using to keep this ClassLoaderData alive.

  oop keep_alive_object() const;

  // Returns true if this class loader data is for a loader going away.

  bool is_unloading() const     {

    assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");

    return _unloading;

  }

  // Used to refcount an anonymous class's CLD in order to

  // indicate their aliveness without a keep_alive_object().

  void inc_keep_alive();

  void dec_keep_alive();

  inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); }

  void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);

  void classes_do(KlassClosure* klass_closure);

  Klass* klasses() { return _klasses; }

  JNIMethodBlock* jmethod_ids() const              { return _jmethod_ids; }

  void set_jmethod_ids(JNIMethodBlock* new_block)  { _jmethod_ids = new_block; }

  void print()                                     { print_on(tty); }

  void print_on(outputStream* out) const PRODUCT_RETURN;

  void print_value()                               { print_value_on(tty); }

  void print_value_on(outputStream* out) const;

  void verify();

  const char* loader_name() const;

  OopHandle add_handle(Handle h);

  void remove_handle(OopHandle h);

  void init_handle_locked(OopHandle& pd, Handle h);  // used for concurrent access to ModuleEntry::_pd field

  void add_class(Klass* k, bool publicize = true);

  void remove_class(Klass* k);

  bool contains_klass(Klass* k);

  void record_dependency(const Klass* to);

  PackageEntryTable* packages() { return _packages; }

  ModuleEntry* unnamed_module() { return _unnamed_module; }

  ModuleEntryTable* modules();

  bool modules_defined() { return (_modules != NULL); }

  // Loaded class dictionary

  Dictionary* dictionary() const { return _dictionary; }

  void add_to_deallocate_list(Metadata* m);

  static ClassLoaderData* class_loader_data(oop loader);

  static ClassLoaderData* class_loader_data_or_null(oop loader);

  static ClassLoaderData* anonymous_class_loader_data(Handle loader);

  TRACE_DEFINE_TRACE_ID_METHODS;

};

// An iterator that distributes Klasses to parallel worker threads.

class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {

 Klass* volatile _next_klass;

 public:

  ClassLoaderDataGraphKlassIteratorAtomic();

  Klass* next_klass();

 private:

  static Klass* next_klass_in_cldg(Klass* klass);

};

class ClassLoaderDataGraphMetaspaceIterator : public StackObj {

  ClassLoaderData* _data;

 public:

  ClassLoaderDataGraphMetaspaceIterator();

  ~ClassLoaderDataGraphMetaspaceIterator();

  bool repeat() { return _data != NULL; }

  Metaspace* get_next() {

    assert(_data != NULL, "Should not be NULL in call to the iterator");

    Metaspace* result = _data->metaspace_or_null();

    _data = _data->next();

    // This result might be NULL for class loaders without metaspace

    // yet.  It would be nice to return only non-null results but

    // there is no guarantee that there will be a non-null result

    // down the list so the caller is going to have to check.

    return result;

  }

};

#endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP