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 /*

  * Copyright (c) 2012, 2017, 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

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 #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 "runtime/mutex.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 the

 // system dictionary, are roots of garbage collection, and provides iterators

 // for root tracing and other GC operations.

 class ClassLoaderData;

 class JNIMethodBlock;

 class Metadebug;

 // GC root for walking class loader data created

 class ClassLoaderDataGraph : public AllStatic {

   friend class ClassLoaderData;

   friend class ClassLoaderDataGraphMetaspaceIterator;

   friend class ClassLoaderDataGraphKlassIteratorAtomic;

   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;

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

   static void post_class_unload_events(void);

   static void clean_metaspaces();

  public:

   static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);

   static void purge();

   static void clear_claimed_marks();

   // oops do

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

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

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

   // cld do

   static void cld_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

   static void classes_do(KlassClosure* klass_closure);

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

   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_alive);

   // 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 void free_deallocate_lists();

   static void dump_on(outputStream * const out) PRODUCT_RETURN;

   static void dump() { dump_on(tty); }

   static void verify();

   static bool unload_list_contains(const void* x);

 #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 Dependencies VALUE_OBJ_CLASS_SPEC {

     objArrayOop _list_head;

     void locked_add(objArrayHandle last,

                     objArrayHandle new_dependency,

                     Thread* THREAD);

    public:

     Dependencies() : _list_head(NULL) {}

     Dependencies(TRAPS) : _list_head(NULL) {

       init(CHECK);

     }

     void add(Handle dependency, TRAPS);

     void init(TRAPS);

     void oops_do(OopClosure* f);

   };

   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* _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);

     void oops_do(OopClosure* f);

   };

   friend class ClassLoaderDataGraph;

   friend class ClassLoaderDataGraphKlassIteratorAtomic;

   friend class ClassLoaderDataGraphMetaspaceIterator;

   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

   Dependencies _dependencies; // holds dependencies from this class loader

                               // data to others.

   Metaspace * _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 _keep_alive;        // if this CLD is kept alive without a keep_alive_object().

   bool _is_anonymous;      // if this CLD is for an 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.

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

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

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

   // 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;

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

   ClassLoaderData* next() const        { return _next; }

   ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);

   ~ClassLoaderData();

   void set_metaspace(Metaspace* m) { _metaspace = m; }

   Mutex* metaspace_lock() const { return _metaspace_lock; }

   // GC interface.

   void clear_claimed()          { _claimed = 0; }

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

   bool claim();

   void unload();

   bool keep_alive() const       { return _keep_alive; }

   void classes_do(void f(Klass*));

   void loaded_classes_do(KlassClosure* klass_closure);

   void classes_do(void f(InstanceKlass*));

   // Deallocate free list during class unloading.

   void free_deallocate_list();

   // Allocate out of this class loader data

   MetaWord* allocate(size_t size);

  public:

   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;

   }

   bool is_anonymous() const { return _is_anonymous; }

   static void init_null_class_loader_data() {

     assert(_the_null_class_loader_data == NULL, "cannot initialize twice");

     assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");

     // We explicitly initialize the Dependencies object at a later phase in the initialization

     _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());

     ClassLoaderDataGraph::_head = _the_null_class_loader_data;

     assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");

     if (DumpSharedSpaces) {

       _the_null_class_loader_data->initialize_shared_metaspaces();

     }

   }

   bool is_the_null_class_loader_data() const {

     return this == _the_null_class_loader_data;

   }

   bool is_ext_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 make sure that this CLD is not unloaded.

   void set_keep_alive(bool value) { _keep_alive = value; }

   unsigned int identity_hash() {

     return _class_loader == NULL ? 0 : _class_loader->identity_hash();

   }

   // Used when tracing from klasses.

   void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);

   void classes_do(KlassClosure* klass_closure);

   JNIMethodBlock* jmethod_ids() const              { return _jmethod_ids; }

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

   void print_value() { print_value_on(tty); }

   void print_value_on(outputStream* out) const;

   void dump(outputStream * const out) PRODUCT_RETURN;

   void verify();

   const char* loader_name();

   jobject add_handle(Handle h);

   void add_class(Klass* k);

   void remove_class(Klass* k);

   bool contains_klass(Klass* k);

   void record_dependency(Klass* to, TRAPS);

   void init_dependencies(TRAPS);

   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(oop loader, TRAPS);

   static void print_loader(ClassLoaderData *loader_data, outputStream *out);

   // CDS support

   Metaspace* ro_metaspace();

   Metaspace* rw_metaspace();

   void initialize_shared_metaspaces();

 };

 // 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