1 /*

     2  * Copyright (c) 2012, 2017, 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 #ifndef SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP

    26 #define SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP

    27 

    28 #include "memory/allocation.hpp"

    29 #include "memory/memRegion.hpp"

    30 #include "memory/metaspace.hpp"

    31 #include "memory/metaspaceCounters.hpp"

    32 #include "oops/oopHandle.hpp"

    33 #include "runtime/mutex.hpp"

    34 #include "trace/traceMacros.hpp"

    35 #include "utilities/growableArray.hpp"

    36 #include "utilities/macros.hpp"

    37 #if INCLUDE_TRACE

    38 #include "utilities/ticks.hpp"

    39 #endif

    40 

    41 //

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

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

    44 // produce.

    45 //

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

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

    48 // the types it defines.

    49 //

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

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

    52 

    53 class ClassLoaderData;

    54 class JNIMethodBlock;

    55 class Metadebug;

    56 class ModuleEntry;

    57 class PackageEntry;

    58 class ModuleEntryTable;

    59 class PackageEntryTable;

    60 class DictionaryEntry;

    61 class Dictionary;

    62 

    63 // GC root for walking class loader data created

    64 

    65 class ClassLoaderDataGraph : public AllStatic {

    66   friend class ClassLoaderData;

    67   friend class ClassLoaderDataGraphMetaspaceIterator;

    68   friend class ClassLoaderDataGraphKlassIteratorAtomic;

    69   friend class ClassLoaderDataGraphKlassIteratorStatic;

    70   friend class VMStructs;

    71  private:

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

    73   static ClassLoaderData* _head;

    74   static ClassLoaderData* _unloading;

    75   // CMS support.

    76   static ClassLoaderData* _saved_head;

    77   static ClassLoaderData* _saved_unloading;

    78   static bool _should_purge;

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

    80   // allocations until class unloading

    81   static bool _metaspace_oom;

    82 

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

    84   static void post_class_unload_events();

    85  public:

    86   static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);

    87   static void purge();

    88   static void clear_claimed_marks();

    89   // oops do

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

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

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

    93   // cld do

    94   static void cld_do(CLDClosure* cl);

    95   static void cld_unloading_do(CLDClosure* cl);

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

    97   static void keep_alive_cld_do(CLDClosure* cl);

    98   static void always_strong_cld_do(CLDClosure* cl);

    99   // klass do

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

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

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

   103   // Walking the ClassLoaderDataGraph also includes anonymous classes.

   104   static void classes_do(KlassClosure* klass_closure);

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

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

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

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

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

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

   111   static void loaded_classes_do(KlassClosure* klass_closure);

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

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

   114 

   115   // dictionary do

   116   // Iterate over all klasses in dictionary, but

   117   // just the classes from defining class loaders.

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

   119   // Added for initialize_itable_for_klass to handle exceptions.

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

   121 

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

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

   124 

   125   // VM_CounterDecay iteration support

   126   static InstanceKlass* try_get_next_class();

   127 

   128   static void verify_dictionary();

   129   static void print_dictionary(outputStream* st);

   130   static void print_dictionary_statistics(outputStream* st);

   131 

   132   // CMS support.

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

   134   static GrowableArray<ClassLoaderData*>* new_clds();

   135 

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

   137   static void purge_if_needed() {

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

   139     if (_should_purge) {

   140       purge();

   141       // reset for next time.

   142       set_should_purge(false);

   143     }

   144   }

   145 

   146   static bool has_metaspace_oom()           { return _metaspace_oom; }

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

   148 

   149   static void dump_on(outputStream * const out) PRODUCT_RETURN;

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

   151   static void verify();

   152   static void print_creation(outputStream* out, Handle loader, ClassLoaderData* cld, TRAPS);

   153 

   154   static bool unload_list_contains(const void* x);

   155 #ifndef PRODUCT

   156   static bool contains_loader_data(ClassLoaderData* loader_data);

   157 #endif

   158 

   159 #if INCLUDE_TRACE

   160  private:

   161   static Ticks _class_unload_time;

   162   static void class_unload_event(Klass* const k);

   163 #endif

   164 };

   165 

   166 // ClassLoaderData class

   167 

   168 class ClassLoaderData : public CHeapObj<mtClass> {

   169   friend class VMStructs;

   170  private:

   171   class Dependencies VALUE_OBJ_CLASS_SPEC {

   172     objArrayOop _list_head;

   173     void locked_add(objArrayHandle last,

   174                     objArrayHandle new_dependency,

   175                     Thread* THREAD);

   176    public:

   177     Dependencies() : _list_head(NULL) {}

   178     Dependencies(TRAPS) : _list_head(NULL) {

   179       init(CHECK);

   180     }

   181     void add(Handle dependency, TRAPS);

   182     void init(TRAPS);

   183     void oops_do(OopClosure* f);

   184   };

   185 

   186   class ChunkedHandleList VALUE_OBJ_CLASS_SPEC {

   187     struct Chunk : public CHeapObj<mtClass> {

   188       static const size_t CAPACITY = 32;

   189 

   190       oop _data[CAPACITY];

   191       volatile juint _size;

   192       Chunk* _next;

   193 

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

   195     };

   196 

   197     Chunk* _head;

   198 

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

   200 

   201    public:

   202     ChunkedHandleList() : _head(NULL) {}

   203     ~ChunkedHandleList();

   204 

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

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

   207     oop* add(oop o);

   208 #ifdef ASSERT

   209     bool contains(oop* p);

   210 #endif

   211     void oops_do(OopClosure* f);

   212   };

   213 

   214   friend class ClassLoaderDataGraph;

   215   friend class ClassLoaderDataGraphKlassIteratorAtomic;

   216   friend class ClassLoaderDataGraphKlassIteratorStatic;

   217   friend class ClassLoaderDataGraphMetaspaceIterator;

   218   friend class MetaDataFactory;

   219   friend class Method;

   220 

   221   static ClassLoaderData * _the_null_class_loader_data;

   222 

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

   224                               // class loader or a canonical class path

   225   Dependencies _dependencies; // holds dependencies from this class loader

   226                               // data to others.

   227 

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

   229                                     // classes in the class loader are allocated.

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

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

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

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

   234                            // Used for anonymous classes and the boot class

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

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

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

   238                            // To avoid applying oop closure more than once.

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

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

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

   242 

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

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

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

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

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

   248 

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

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

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

   252   JNIMethodBlock*                  _jmethod_ids;

   253 

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

   255   // this class loader isn't unloaded itself.

   256   GrowableArray<Metadata*>*      _deallocate_list;

   257 

   258   // Support for walking class loader data objects

   259   ClassLoaderData* _next; /// Next loader_datas created

   260 

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

   262   // class loader for now).

   263   static Metaspace* _ro_metaspace;

   264   static Metaspace* _rw_metaspace;

   265 

   266   TRACE_DEFINE_TRACE_ID_FIELD;

   267 

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

   269   ClassLoaderData* next() const        { return _next; }

   270 

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

   272   ~ClassLoaderData();

   273 

   274   // GC interface.

   275   void clear_claimed()          { _claimed = 0; }

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

   277   bool claim();

   278 

   279   void unload();

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

   281   void classes_do(void f(Klass*));

   282   void loaded_classes_do(KlassClosure* klass_closure);

   283   void classes_do(void f(InstanceKlass*));

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

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

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

   287 

   288   // Deallocate free list during class unloading.

   289   void free_deallocate_list();

   290 

   291   // Allocate out of this class loader data

   292   MetaWord* allocate(size_t size);

   293 

   294   Dictionary* create_dictionary();

   295  public:

   296 

   297   bool is_alive(BoolObjectClosure* is_alive_closure) const;

   298 

   299   // Accessors

   300   Metaspace* metaspace_or_null() const     { return _metaspace; }

   301 

   302   static ClassLoaderData* the_null_class_loader_data() {

   303     return _the_null_class_loader_data;

   304   }

   305 

   306   Mutex* metaspace_lock() const { return _metaspace_lock; }

   307 

   308   bool is_anonymous() const { return _is_anonymous; }

   309 

   310   static void init_null_class_loader_data() {

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

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

   313 

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

   315     _the_null_class_loader_data = new ClassLoaderData(Handle(), false, Dependencies());

   316     ClassLoaderDataGraph::_head = _the_null_class_loader_data;

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

   318   }

   319 

   320   bool is_the_null_class_loader_data() const {

   321     return this == _the_null_class_loader_data;

   322   }

   323   bool is_system_class_loader_data() const;

   324   bool is_platform_class_loader_data() const;

   325   bool is_builtin_class_loader_data() const;

   326 

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

   328   // method will allocate a Metaspace if needed.

   329   Metaspace* metaspace_non_null();

   330 

   331   oop class_loader() const      { return _class_loader; }

   332 

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

   334   oop keep_alive_object() const;

   335 

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

   337   bool is_unloading() const     {

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

   339     return _unloading;

   340   }

   341 

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

   343   // indicate their aliveness without a keep_alive_object().

   344   void inc_keep_alive();

   345   void dec_keep_alive();

   346 

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

   348 

   349   // Used when tracing from klasses.

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

   351 

   352   void classes_do(KlassClosure* klass_closure);

   353   Klass* klasses() { return _klasses; }

   354 

   355   JNIMethodBlock* jmethod_ids() const              { return _jmethod_ids; }

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

   357 

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

   359   void print_on(outputStream* out) const;

   360   void print_value()                               { print_value_on(tty); }

   361   void print_value_on(outputStream* out) const;

   362   void dump(outputStream * const out) PRODUCT_RETURN;

   363   void verify();

   364   const char* loader_name();

   365 

   366   OopHandle add_handle(Handle h);

   367   void remove_handle(OopHandle h);

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

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

   370   void remove_class(Klass* k);

   371   bool contains_klass(Klass* k);

   372   void record_dependency(const Klass* to, TRAPS);

   373   void init_dependencies(TRAPS);

   374   PackageEntryTable* packages() { return _packages; }

   375   ModuleEntry* unnamed_module() { return _unnamed_module; }

   376   ModuleEntryTable* modules();

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

   378 

   379   // Loaded class dictionary

   380   Dictionary* dictionary() const { return _dictionary; }

   381 

   382   void add_to_deallocate_list(Metadata* m);

   383 

   384   static ClassLoaderData* class_loader_data(oop loader);

   385   static ClassLoaderData* class_loader_data_or_null(oop loader);

   386   static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);

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

   388 

   389   TRACE_DEFINE_TRACE_ID_METHODS;

   390 };

   391 

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

   393 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {

   394  Klass* volatile _next_klass;

   395  public:

   396   ClassLoaderDataGraphKlassIteratorAtomic();

   397   Klass* next_klass();

   398  private:

   399   static Klass* next_klass_in_cldg(Klass* klass);

   400 };

   401 

   402 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {

   403   ClassLoaderData* _data;

   404  public:

   405   ClassLoaderDataGraphMetaspaceIterator();

   406   ~ClassLoaderDataGraphMetaspaceIterator();

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

   408   Metaspace* get_next() {

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

   410     Metaspace* result = _data->metaspace_or_null();

   411     _data = _data->next();

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

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

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

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

   416     return result;

   417   }

   418 };

   419 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP