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.
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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).
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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, bool must_claim);
91 static void keep_alive_oops_do(OopClosure* blk, bool must_claim);
92 static void always_strong_oops_do(OopClosure* blk, 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 int resize_if_needed();
147
148 static bool has_metaspace_oom() { return _metaspace_oom; }
149 static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
150
151 static void dump_on(outputStream * const out) PRODUCT_RETURN;
152 static void dump() { dump_on(tty); }
153 static void verify();
154 static void print_creation(outputStream* out, Handle loader, ClassLoaderData* cld, TRAPS);
155
156 static bool unload_list_contains(const void* x);
157 #ifndef PRODUCT
158 static bool contains_loader_data(ClassLoaderData* loader_data);
159 #endif
160
161 #if INCLUDE_TRACE
162 private:
163 static Ticks _class_unload_time;
164 static void class_unload_event(Klass* const k);
165 #endif
166 };
167
168 // ClassLoaderData class
169
170 class ClassLoaderData : public CHeapObj<mtClass> {
171 friend class VMStructs;
172 private:
173 class Dependencies VALUE_OBJ_CLASS_SPEC {
174 objArrayOop _list_head;
175 void locked_add(objArrayHandle last,
176 objArrayHandle new_dependency,
177 Thread* THREAD);
178 public:
179 Dependencies() : _list_head(NULL) {}
180 Dependencies(TRAPS) : _list_head(NULL) {
181 init(CHECK);
182 }
183 void add(Handle dependency, TRAPS);
184 void init(TRAPS);
185 void oops_do(OopClosure* f);
186 };
187
188 class ChunkedHandleList VALUE_OBJ_CLASS_SPEC {
189 struct Chunk : public CHeapObj<mtClass> {
190 static const size_t CAPACITY = 32;
191
192 oop _data[CAPACITY];
193 volatile juint _size;
194 Chunk* _next;
195
196 Chunk(Chunk* c) : _next(c), _size(0) { }
197 };
198
199 Chunk* volatile _head;
200
201 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
202
203 public:
204 ChunkedHandleList() : _head(NULL) {}
205 ~ChunkedHandleList();
206
207 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
208 // However, multiple threads can execute oops_do concurrently with add.
209 oop* add(oop o);
210 #ifdef ASSERT
211 bool contains(oop* p);
212 #endif
213 void oops_do(OopClosure* f);
214 };
215
216 friend class ClassLoaderDataGraph;
217 friend class ClassLoaderDataGraphKlassIteratorAtomic;
218 friend class ClassLoaderDataGraphKlassIteratorStatic;
219 friend class ClassLoaderDataGraphMetaspaceIterator;
220 friend class MetaDataFactory;
221 friend class Method;
222
223 static ClassLoaderData * _the_null_class_loader_data;
224
225 oop _class_loader; // oop used to uniquely identify a class loader
226 // class loader or a canonical class path
227 Dependencies _dependencies; // holds dependencies from this class loader
228 // data to others.
229
230 Metaspace * volatile _metaspace; // Meta-space where meta-data defined by the
231 // classes in the class loader are allocated.
232 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
233 bool _unloading; // true if this class loader goes away
234 bool _is_anonymous; // if this CLD is for an anonymous class
235
236 // Remembered sets support for the oops in the class loader data.
237 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
238 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
239
240 s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object().
241 // Used for anonymous classes and the boot class
242 // loader. _keep_alive does not need to be volatile or
243 // atomic since there is one unique CLD per anonymous class.
244
245 volatile int _claimed; // true if claimed, for example during GC traces.
246 // To avoid applying oop closure more than once.
247 // Has to be an int because we cas it.
248 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
249 // have the same life cycle of the corresponding ClassLoader.
250
251 Klass* volatile _klasses; // The classes defined by the class loader.
252 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
253 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
254 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
255 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
256
257 // These method IDs are created for the class loader and set to NULL when the
258 // class loader is unloaded. They are rarely freed, only for redefine classes
259 // and if they lose a data race in InstanceKlass.
260 JNIMethodBlock* _jmethod_ids;
261
262 // Metadata to be deallocated when it's safe at class unloading, when
263 // this class loader isn't unloaded itself.
264 GrowableArray<Metadata*>* _deallocate_list;
265
266 // Support for walking class loader data objects
267 ClassLoaderData* _next; /// Next loader_datas created
268
269 // ReadOnly and ReadWrite metaspaces (static because only on the null
270 // class loader for now).
271 static Metaspace* _ro_metaspace;
272 static Metaspace* _rw_metaspace;
273
274 TRACE_DEFINE_TRACE_ID_FIELD;
275
276 void set_next(ClassLoaderData* next) { _next = next; }
277 ClassLoaderData* next() const { return _next; }
278
279 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
280 ~ClassLoaderData();
281
282 // GC interface.
283 void clear_claimed() { _claimed = 0; }
284 bool claimed() const { return _claimed == 1; }
285 bool claim();
286
287 // The CLD are not placed in the Heap, so the Card Table or
288 // the Mod Union Table can't be used to mark when CLD have modified oops.
289 // The CT and MUT bits saves this information for the whole class loader data.
290 void clear_modified_oops() { _modified_oops = false; }
291 public:
292 void record_modified_oops() { _modified_oops = true; }
293 bool has_modified_oops() { return _modified_oops; }
294
295 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
296 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
297 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
298 private:
299
300 void unload();
301 bool keep_alive() const { return _keep_alive > 0; }
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 unload_deallocate_list(); // 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 public:
318
319 bool is_alive(BoolObjectClosure* is_alive_closure) const;
320
321 // Accessors
322 Metaspace* metaspace_or_null() const { return _metaspace; }
323
324 static ClassLoaderData* the_null_class_loader_data() {
325 return _the_null_class_loader_data;
326 }
327
328 Mutex* metaspace_lock() const { return _metaspace_lock; }
329
330 bool is_anonymous() const { return _is_anonymous; }
331
332 static void init_null_class_loader_data() {
333 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
334 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
335
336 // We explicitly initialize the Dependencies object at a later phase in the initialization
337 _the_null_class_loader_data = new ClassLoaderData(Handle(), false, Dependencies());
338 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
339 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
340 }
341
342 bool is_the_null_class_loader_data() const {
343 return this == _the_null_class_loader_data;
344 }
345 bool is_system_class_loader_data() const;
346 bool is_platform_class_loader_data() const;
347 bool is_builtin_class_loader_data() const;
348
349 // The Metaspace is created lazily so may be NULL. This
350 // method will allocate a Metaspace if needed.
351 Metaspace* metaspace_non_null();
352
353 oop class_loader() const { return _class_loader; }
354
355 // The object the GC is using to keep this ClassLoaderData alive.
356 oop keep_alive_object() const;
357
358 // Returns true if this class loader data is for a loader going away.
359 bool is_unloading() const {
360 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
361 return _unloading;
362 }
363
364 // Used to refcount an anonymous class's CLD in order to
365 // indicate their aliveness without a keep_alive_object().
366 void inc_keep_alive();
367 void dec_keep_alive();
368
369 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); }
370
371 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
372
373 void classes_do(KlassClosure* klass_closure);
374 Klass* klasses() { return _klasses; }
375
376 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
377 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
378
379 void print() { print_on(tty); }
380 void print_on(outputStream* out) const;
381 void print_value() { print_value_on(tty); }
382 void print_value_on(outputStream* out) const;
383 void dump(outputStream * const out) PRODUCT_RETURN;
384 void verify();
385 const char* loader_name();
386
387 OopHandle add_handle(Handle h);
388 void remove_handle(OopHandle h);
389 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
390 void add_class(Klass* k, bool publicize = true);
391 void remove_class(Klass* k);
392 bool contains_klass(Klass* k);
393 void record_dependency(const Klass* to, TRAPS);
394 void init_dependencies(TRAPS);
395 PackageEntryTable* packages() { return _packages; }
396 ModuleEntry* unnamed_module() { return _unnamed_module; }
397 ModuleEntryTable* modules();
398 bool modules_defined() { return (_modules != NULL); }
399
400 // Loaded class dictionary
401 Dictionary* dictionary() const { return _dictionary; }
402
403 void add_to_deallocate_list(Metadata* m);
404
405 static ClassLoaderData* class_loader_data(oop loader);
406 static ClassLoaderData* class_loader_data_or_null(oop loader);
407 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
408 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
409
410 TRACE_DEFINE_TRACE_ID_METHODS;
411 };
412
413 // An iterator that distributes Klasses to parallel worker threads.
414 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
415 Klass* volatile _next_klass;
416 public:
417 ClassLoaderDataGraphKlassIteratorAtomic();
418 Klass* next_klass();
419 private:
420 static Klass* next_klass_in_cldg(Klass* klass);
421 };
422
423 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
424 ClassLoaderData* _data;
425 public:
426 ClassLoaderDataGraphMetaspaceIterator();
427 ~ClassLoaderDataGraphMetaspaceIterator();
428 bool repeat() { return _data != NULL; }
429 Metaspace* get_next() {
430 assert(_data != NULL, "Should not be NULL in call to the iterator");
431 Metaspace* result = _data->metaspace_or_null();
432 _data = _data->next();
433 // This result might be NULL for class loaders without metaspace
434 // yet. It would be nice to return only non-null results but
435 // there is no guarantee that there will be a non-null result
436 // down the list so the caller is going to have to check.
437 return result;
438 }
439 };
440 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP