1 /*
   2  * Copyright (c) 2012, 2018, 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 "oops/oopHandle.hpp"
  32 #include "oops/weakHandle.hpp"
  33 #include "runtime/mutex.hpp"
  34 #include "utilities/growableArray.hpp"
  35 #include "utilities/macros.hpp"
  36 #if INCLUDE_JFR
  37 #include "jfr/support/jfrTraceIdExtension.hpp"
  38 #endif
  39 
  40 // external name (synthetic) for the primordial "bootstrap" class loader instance
  41 #define BOOTSTRAP_LOADER_NAME "bootstrap"
  42 #define BOOTSTRAP_LOADER_NAME_LEN 9
  43 
  44 //
  45 // A class loader represents a linkset. Conceptually, a linkset identifies
  46 // the complete transitive closure of resolved links that a dynamic linker can
  47 // produce.
  48 //
  49 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
  50 // used by the dynamic linker to allocate the runtime representation of all
  51 // the types it defines.
  52 //
  53 // ClassLoaderData are stored in the runtime representation of classes,
  54 // and provides iterators for root tracing and other GC operations.
  55 
  56 class ClassLoaderData;
  57 class JNIMethodBlock;
  58 class Metadebug;
  59 class ModuleEntry;
  60 class PackageEntry;
  61 class ModuleEntryTable;
  62 class PackageEntryTable;
  63 class DictionaryEntry;
  64 class Dictionary;
  65 
  66 // GC root for walking class loader data created
  67 
  68 class ClassLoaderDataGraph : public AllStatic {
  69   friend class ClassLoaderData;
  70   friend class ClassLoaderDataGraphMetaspaceIterator;
  71   friend class ClassLoaderDataGraphKlassIteratorAtomic;
  72   friend class ClassLoaderDataGraphKlassIteratorStatic;
  73   friend class VMStructs;
  74  private:
  75   // All CLDs (except the null CLD) can be reached by walking _head->_next->...
  76   static ClassLoaderData* _head;
  77   static ClassLoaderData* _unloading;
  78   // CMS support.
  79   static ClassLoaderData* _saved_head;
  80   static ClassLoaderData* _saved_unloading;
  81   static bool _should_purge;
  82 
  83   // Set if there's anything to purge in the deallocate lists or previous versions
  84   // during a safepoint after class unloading in a full GC.
  85   static bool _should_clean_deallocate_lists;
  86   static bool _safepoint_cleanup_needed;
  87 
  88   // OOM has been seen in metaspace allocation. Used to prevent some
  89   // allocations until class unloading
  90   static bool _metaspace_oom;
  91 
  92   static volatile size_t  _num_instance_classes;
  93   static volatile size_t  _num_array_classes;
  94 
  95   static ClassLoaderData* add_to_graph(Handle class_loader, bool is_unsafe_anonymous);
  96   static ClassLoaderData* add(Handle class_loader, bool is_unsafe_anonymous);
  97 
  98  public:
  99   static ClassLoaderData* find_or_create(Handle class_loader);
 100   static void clean_module_and_package_info();
 101   static void purge();
 102   static void clear_claimed_marks();
 103   // Iteration through CLDG inside a safepoint; GC support
 104   static void cld_do(CLDClosure* cl);
 105   static void cld_unloading_do(CLDClosure* cl);
 106   static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);

 107   static void always_strong_cld_do(CLDClosure* cl);
 108   // klass do
 109   // Walking classes through the ClassLoaderDataGraph include array classes.  It also includes
 110   // classes that are allocated but not loaded, classes that have errors, and scratch classes
 111   // for redefinition.  These classes are removed during the next class unloading.
 112   // Walking the ClassLoaderDataGraph also includes unsafe anonymous classes.
 113   static void classes_do(KlassClosure* klass_closure);
 114   static void classes_do(void f(Klass* const));
 115   static void methods_do(void f(Method*));
 116   static void modules_do(void f(ModuleEntry*));
 117   static void modules_unloading_do(void f(ModuleEntry*));
 118   static void packages_do(void f(PackageEntry*));
 119   static void packages_unloading_do(void f(PackageEntry*));
 120   static void loaded_classes_do(KlassClosure* klass_closure);
 121   static void classes_unloading_do(void f(Klass* const));
 122   static bool do_unloading(bool do_cleaning);
 123 
 124   // Expose state to avoid logging overhead in safepoint cleanup tasks.
 125   static inline bool should_clean_metaspaces_and_reset();
 126   static void set_should_clean_deallocate_lists() { _should_clean_deallocate_lists = true; }
 127   static void clean_deallocate_lists(bool purge_previous_versions);
 128   static void walk_metadata_and_clean_metaspaces();
 129 
 130   // dictionary do
 131   // Iterate over all klasses in dictionary, but
 132   // just the classes from defining class loaders.
 133   static void dictionary_classes_do(void f(InstanceKlass*));
 134   // Added for initialize_itable_for_klass to handle exceptions.
 135   static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS);
 136 
 137   // Iterate all classes and their class loaders, including initiating class loaders.
 138   static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*));
 139 
 140   // VM_CounterDecay iteration support
 141   static InstanceKlass* try_get_next_class();
 142 
 143   static void verify_dictionary();
 144   static void print_dictionary(outputStream* st);
 145   static void print_dictionary_statistics(outputStream* st);
 146 
 147   // CMS support.
 148   static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
 149   static GrowableArray<ClassLoaderData*>* new_clds();
 150 
 151   static void set_should_purge(bool b) { _should_purge = b; }
 152   static void purge_if_needed() {
 153     // Only purge the CLDG for CMS if concurrent sweep is complete.
 154     if (_should_purge) {
 155       purge();
 156       // reset for next time.
 157       set_should_purge(false);
 158     }
 159   }
 160 
 161   static int resize_if_needed();
 162 
 163   static bool has_metaspace_oom()           { return _metaspace_oom; }
 164   static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
 165 
 166   static void print_on(outputStream * const out) PRODUCT_RETURN;
 167   static void print() { print_on(tty); }
 168   static void verify();
 169 
 170   // instance and array class counters
 171   static inline size_t num_instance_classes();
 172   static inline size_t num_array_classes();
 173   static inline void inc_instance_classes(size_t count);
 174   static inline void dec_instance_classes(size_t count);
 175   static inline void inc_array_classes(size_t count);
 176   static inline void dec_array_classes(size_t count);
 177 
 178 #ifndef PRODUCT
 179   static bool contains_loader_data(ClassLoaderData* loader_data);
 180 #endif
 181 };
 182 
 183 // ClassLoaderData class
 184 
 185 class ClassLoaderData : public CHeapObj<mtClass> {
 186   friend class VMStructs;
 187 
 188  private:
 189   class ChunkedHandleList {
 190     struct Chunk : public CHeapObj<mtClass> {
 191       static const size_t CAPACITY = 32;
 192 
 193       oop _data[CAPACITY];
 194       volatile juint _size;
 195       Chunk* _next;
 196 
 197       Chunk(Chunk* c) : _size(0), _next(c) { }
 198     };
 199 
 200     Chunk* volatile _head;
 201 
 202     void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
 203 
 204    public:
 205     ChunkedHandleList() : _head(NULL) {}
 206     ~ChunkedHandleList();
 207 
 208     // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
 209     // However, multiple threads can execute oops_do concurrently with add.
 210     oop* add(oop o);
 211     bool contains(oop p);
 212     NOT_PRODUCT(bool owner_of(oop* p);)
 213     void oops_do(OopClosure* f);
 214 
 215     int count() const;
 216   };
 217 
 218   friend class ClassLoaderDataGraph;
 219   friend class ClassLoaderDataGraphKlassIteratorAtomic;
 220   friend class ClassLoaderDataGraphKlassIteratorStatic;
 221   friend class ClassLoaderDataGraphMetaspaceIterator;
 222   friend class Klass;
 223   friend class MetaDataFactory;
 224   friend class Method;
 225 
 226   static ClassLoaderData * _the_null_class_loader_data;
 227 
 228   WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader
 229   OopHandle _class_loader;    // The instance of java/lang/ClassLoader associated with
 230                               // this ClassLoaderData
 231 
 232   ClassLoaderMetaspace * volatile _metaspace;  // Meta-space where meta-data defined by the
 233                                     // classes in the class loader are allocated.
 234   Mutex* _metaspace_lock;  // Locks the metaspace for allocations and setup.
 235   bool _unloading;         // true if this class loader goes away
 236   bool _is_unsafe_anonymous; // CLD is dedicated to one class and that class determines the CLDs lifecycle.
 237                              // For example, an unsafe anonymous class.
 238 
 239   // Remembered sets support for the oops in the class loader data.
 240   bool _modified_oops;             // Card Table Equivalent (YC/CMS support)
 241   bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
 242 
 243   s2 _keep_alive;          // if this CLD is kept alive.
 244                            // Used for unsafe anonymous classes and the boot class
 245                            // loader. _keep_alive does not need to be volatile or
 246                            // atomic since there is one unique CLD per unsafe anonymous class.
 247 
 248   volatile int _claimed;   // true if claimed, for example during GC traces.
 249                            // To avoid applying oop closure more than once.
 250                            // Has to be an int because we cas it.
 251   ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
 252                               // have the same life cycle of the corresponding ClassLoader.
 253 
 254   NOT_PRODUCT(volatile int _dependency_count;)  // number of class loader dependencies
 255 
 256   Klass* volatile _klasses;              // The classes defined by the class loader.
 257   PackageEntryTable* volatile _packages; // The packages defined by the class loader.
 258   ModuleEntryTable*  volatile _modules;  // The modules defined by the class loader.
 259   ModuleEntry* _unnamed_module;          // This class loader's unnamed module.
 260   Dictionary*  _dictionary;              // The loaded InstanceKlasses, including initiated by this class loader
 261 
 262   // These method IDs are created for the class loader and set to NULL when the
 263   // class loader is unloaded.  They are rarely freed, only for redefine classes
 264   // and if they lose a data race in InstanceKlass.
 265   JNIMethodBlock*                  _jmethod_ids;
 266 
 267   // Metadata to be deallocated when it's safe at class unloading, when
 268   // this class loader isn't unloaded itself.
 269   GrowableArray<Metadata*>*      _deallocate_list;
 270 
 271   // Support for walking class loader data objects
 272   ClassLoaderData* _next; /// Next loader_datas created
 273 
 274   Klass*  _class_loader_klass;
 275   Symbol* _name;
 276   Symbol* _name_and_id;
 277   JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
 278 
 279   void set_next(ClassLoaderData* next) { _next = next; }
 280   ClassLoaderData* next() const        { return _next; }
 281 
 282   ClassLoaderData(Handle h_class_loader, bool is_unsafe_anonymous);
 283   ~ClassLoaderData();
 284 
 285   // The CLD are not placed in the Heap, so the Card Table or
 286   // the Mod Union Table can't be used to mark when CLD have modified oops.
 287   // The CT and MUT bits saves this information for the whole class loader data.
 288   void clear_modified_oops()             { _modified_oops = false; }
 289  public:
 290   void record_modified_oops()            { _modified_oops = true; }
 291   bool has_modified_oops()               { return _modified_oops; }
 292 
 293   void accumulate_modified_oops()        { if (has_modified_oops()) _accumulated_modified_oops = true; }
 294   void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
 295   bool has_accumulated_modified_oops()   { return _accumulated_modified_oops; }
 296  private:
 297 
 298   void unload();
 299   bool keep_alive() const       { return _keep_alive > 0; }
 300 
 301   oop holder_phantom() const;
 302   void classes_do(void f(Klass*));
 303   void loaded_classes_do(KlassClosure* klass_closure);
 304   void classes_do(void f(InstanceKlass*));
 305   void methods_do(void f(Method*));
 306   void modules_do(void f(ModuleEntry*));
 307   void packages_do(void f(PackageEntry*));
 308 
 309   // Deallocate free list during class unloading.
 310   void free_deallocate_list();                      // for the classes that are not unloaded
 311   void free_deallocate_list_C_heap_structures();    // for the classes that are unloaded
 312 
 313   // Allocate out of this class loader data
 314   MetaWord* allocate(size_t size);
 315 
 316   Dictionary* create_dictionary();
 317 
 318   void initialize_name(Handle class_loader);
 319  public:
 320   // GC interface.
 321   void clear_claimed() { _claimed = 0; }
 322   bool claimed() const { return _claimed == 1; }
 323   bool claim();
 324 
 325   bool is_alive() const;
 326 
 327   // Accessors
 328   ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
 329 
 330   static ClassLoaderData* the_null_class_loader_data() {
 331     return _the_null_class_loader_data;
 332   }
 333 
 334   Mutex* metaspace_lock() const { return _metaspace_lock; }
 335 
 336   bool is_unsafe_anonymous() const { return _is_unsafe_anonymous; }
 337 
 338   static void init_null_class_loader_data();
 339 
 340   bool is_the_null_class_loader_data() const {
 341     return this == _the_null_class_loader_data;
 342   }
 343 
 344   // Returns true if this class loader data is for the system class loader.
 345   // (Note that the class loader data may be unsafe anonymous.)
 346   bool is_system_class_loader_data() const;
 347 
 348   // Returns true if this class loader data is for the platform class loader.
 349   // (Note that the class loader data may be unsafe anonymous.)
 350   bool is_platform_class_loader_data() const;
 351 
 352   // Returns true if this class loader data is for the boot class loader.
 353   // (Note that the class loader data may be unsafe anonymous.)
 354   inline bool is_boot_class_loader_data() const;
 355 
 356   bool is_builtin_class_loader_data() const;
 357   bool is_permanent_class_loader_data() const;
 358 
 359   // The Metaspace is created lazily so may be NULL.  This
 360   // method will allocate a Metaspace if needed.
 361   ClassLoaderMetaspace* metaspace_non_null();
 362 
 363   inline oop class_loader() const;
 364 
 365   // Returns true if this class loader data is for a loader going away.
 366   bool is_unloading() const     {
 367     assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
 368     return _unloading;
 369   }
 370 
 371   // Used to refcount an unsafe anonymous class's CLD in order to
 372   // indicate their aliveness.
 373   void inc_keep_alive();
 374   void dec_keep_alive();
 375 
 376   void initialize_holder(Handle holder);
 377 
 378   void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
 379 
 380   void classes_do(KlassClosure* klass_closure);
 381   Klass* klasses() { return _klasses; }
 382 
 383   JNIMethodBlock* jmethod_ids() const              { return _jmethod_ids; }
 384   void set_jmethod_ids(JNIMethodBlock* new_block)  { _jmethod_ids = new_block; }
 385 
 386   void print()                                     { print_on(tty); }
 387   void print_on(outputStream* out) const PRODUCT_RETURN;
 388   void print_value()                               { print_value_on(tty); }
 389   void print_value_on(outputStream* out) const;
 390   void verify();
 391 
 392   OopHandle add_handle(Handle h);
 393   void remove_handle(OopHandle h);
 394   void init_handle_locked(OopHandle& pd, Handle h);  // used for concurrent access to ModuleEntry::_pd field
 395   void add_class(Klass* k, bool publicize = true);
 396   void remove_class(Klass* k);
 397   bool contains_klass(Klass* k);
 398   void record_dependency(const Klass* to);
 399   PackageEntryTable* packages() { return _packages; }
 400   ModuleEntry* unnamed_module() { return _unnamed_module; }
 401   ModuleEntryTable* modules();
 402   bool modules_defined() { return (_modules != NULL); }
 403 
 404   // Loaded class dictionary
 405   Dictionary* dictionary() const { return _dictionary; }
 406 
 407   void add_to_deallocate_list(Metadata* m);
 408 
 409   static ClassLoaderData* class_loader_data(oop loader);
 410   static ClassLoaderData* class_loader_data_or_null(oop loader);
 411   static ClassLoaderData* unsafe_anonymous_class_loader_data(Handle loader);
 412 
 413   // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'.
 414   // Also works if unloading.
 415   Klass* class_loader_klass() const { return _class_loader_klass; }
 416 
 417   // Returns the class loader's explict name as specified during
 418   // construction or the class loader's qualified class name.
 419   // Works during unloading.
 420   const char* loader_name() const;
 421   // Returns the explicitly specified class loader name or NULL.
 422   Symbol* name() const { return _name; }
 423 
 424   // Obtain the class loader's _name_and_id, works during unloading.
 425   const char* loader_name_and_id() const;
 426   Symbol* name_and_id() const { return _name_and_id; }
 427 
 428   JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
 429 };
 430 
 431 // An iterator that distributes Klasses to parallel worker threads.
 432 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
 433  Klass* volatile _next_klass;
 434  public:
 435   ClassLoaderDataGraphKlassIteratorAtomic();
 436   Klass* next_klass();
 437  private:
 438   static Klass* next_klass_in_cldg(Klass* klass);
 439 };
 440 
 441 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
 442   ClassLoaderData* _data;
 443  public:
 444   ClassLoaderDataGraphMetaspaceIterator();
 445   ~ClassLoaderDataGraphMetaspaceIterator();
 446   bool repeat() { return _data != NULL; }
 447   ClassLoaderMetaspace* get_next() {
 448     assert(_data != NULL, "Should not be NULL in call to the iterator");
 449     ClassLoaderMetaspace* result = _data->metaspace_or_null();
 450     _data = _data->next();
 451     // This result might be NULL for class loaders without metaspace
 452     // yet.  It would be nice to return only non-null results but
 453     // there is no guarantee that there will be a non-null result
 454     // down the list so the caller is going to have to check.
 455     return result;
 456   }
 457 };
 458 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP
--- EOF ---