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
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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 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* volatile _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
234 // Remembered sets support for the oops in the class loader data.
235 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
236 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
237
238 s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object().
239 // Used for anonymous classes and the boot class
240 // loader. _keep_alive does not need to be volatile or
241 // atomic since there is one unique CLD per anonymous class.
242
243 volatile int _claimed; // true if claimed, for example during GC traces.
244 // To avoid applying oop closure more than once.
245 // Has to be an int because we cas it.
246 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
247 // have the same life cycle of the corresponding ClassLoader.
248
249 Klass* volatile _klasses; // The classes defined by the class loader.
250 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
251 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
252 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
253 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
254
255 // These method IDs are created for the class loader and set to NULL when the
256 // class loader is unloaded. They are rarely freed, only for redefine classes
257 // and if they lose a data race in InstanceKlass.
258 JNIMethodBlock* _jmethod_ids;
259
260 // Metadata to be deallocated when it's safe at class unloading, when
261 // this class loader isn't unloaded itself.
262 GrowableArray<Metadata*>* _deallocate_list;
263
264 // Support for walking class loader data objects
265 ClassLoaderData* _next; /// Next loader_datas created
266
267 // ReadOnly and ReadWrite metaspaces (static because only on the null
268 // class loader for now).
269 static Metaspace* _ro_metaspace;
270 static Metaspace* _rw_metaspace;
271
272 TRACE_DEFINE_TRACE_ID_FIELD;
273
274 void set_next(ClassLoaderData* next) { _next = next; }
275 ClassLoaderData* next() const { return _next; }
276
277 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
278 ~ClassLoaderData();
279
280 // GC interface.
281 void clear_claimed() { _claimed = 0; }
282 bool claimed() const { return _claimed == 1; }
283 bool claim();
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 void classes_do(void f(Klass*));
301 void loaded_classes_do(KlassClosure* klass_closure);
302 void classes_do(void f(InstanceKlass*));
303 void methods_do(void f(Method*));
304 void modules_do(void f(ModuleEntry*));
305 void packages_do(void f(PackageEntry*));
306
307 // Deallocate free list during class unloading.
308 void free_deallocate_list();
309
310 // Allocate out of this class loader data
311 MetaWord* allocate(size_t size);
312
313 Dictionary* create_dictionary();
314 public:
315
316 bool is_alive(BoolObjectClosure* is_alive_closure) const;
317
318 // Accessors
319 Metaspace* metaspace_or_null() const { return _metaspace; }
320
321 static ClassLoaderData* the_null_class_loader_data() {
322 return _the_null_class_loader_data;
323 }
324
325 Mutex* metaspace_lock() const { return _metaspace_lock; }
326
327 bool is_anonymous() const { return _is_anonymous; }
328
329 static void init_null_class_loader_data() {
330 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
331 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
332
333 // We explicitly initialize the Dependencies object at a later phase in the initialization
334 _the_null_class_loader_data = new ClassLoaderData(Handle(), false, Dependencies());
335 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
336 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
337 }
338
339 bool is_the_null_class_loader_data() const {
340 return this == _the_null_class_loader_data;
341 }
342 bool is_system_class_loader_data() const;
343 bool is_platform_class_loader_data() const;
344 bool is_builtin_class_loader_data() const;
345
346 // The Metaspace is created lazily so may be NULL. This
347 // method will allocate a Metaspace if needed.
348 Metaspace* metaspace_non_null();
349
350 oop class_loader() const { return _class_loader; }
351
352 // The object the GC is using to keep this ClassLoaderData alive.
353 oop keep_alive_object() const;
354
355 // Returns true if this class loader data is for a loader going away.
356 bool is_unloading() const {
357 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
358 return _unloading;
359 }
360
361 // Used to refcount an anonymous class's CLD in order to
362 // indicate their aliveness without a keep_alive_object().
363 void inc_keep_alive();
364 void dec_keep_alive();
365
366 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); }
367
368 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
369
370 void classes_do(KlassClosure* klass_closure);
371 Klass* klasses() { return _klasses; }
372
373 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
374 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
375
376 void print() { print_on(tty); }
377 void print_on(outputStream* out) const;
378 void print_value() { print_value_on(tty); }
379 void print_value_on(outputStream* out) const;
380 void dump(outputStream * const out) PRODUCT_RETURN;
381 void verify();
382 const char* loader_name();
383
384 OopHandle add_handle(Handle h);
385 void remove_handle(OopHandle h);
386 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
387 void add_class(Klass* k, bool publicize = true);
388 void remove_class(Klass* k);
389 bool contains_klass(Klass* k);
390 void record_dependency(const Klass* to, TRAPS);
391 void init_dependencies(TRAPS);
392 PackageEntryTable* packages() { return _packages; }
393 ModuleEntry* unnamed_module() { return _unnamed_module; }
394 ModuleEntryTable* modules();
395 bool modules_defined() { return (_modules != NULL); }
396
397 // Loaded class dictionary
398 Dictionary* dictionary() const { return _dictionary; }
399
400 void add_to_deallocate_list(Metadata* m);
401
402 static ClassLoaderData* class_loader_data(oop loader);
403 static ClassLoaderData* class_loader_data_or_null(oop loader);
404 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
405 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
406
407 TRACE_DEFINE_TRACE_ID_METHODS;
408 };
409
410 // An iterator that distributes Klasses to parallel worker threads.
411 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
412 Klass* volatile _next_klass;
413 public:
414 ClassLoaderDataGraphKlassIteratorAtomic();
415 Klass* next_klass();
416 private:
417 static Klass* next_klass_in_cldg(Klass* klass);
418 };
419
420 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
421 ClassLoaderData* _data;
422 public:
423 ClassLoaderDataGraphMetaspaceIterator();
424 ~ClassLoaderDataGraphMetaspaceIterator();
425 bool repeat() { return _data != NULL; }
426 Metaspace* get_next() {
427 assert(_data != NULL, "Should not be NULL in call to the iterator");
428 Metaspace* result = _data->metaspace_or_null();
429 _data = _data->next();
430 // This result might be NULL for class loaders without metaspace
431 // yet. It would be nice to return only non-null results but
432 // there is no guarantee that there will be a non-null result
433 // down the list so the caller is going to have to check.
434 return result;
435 }
436 };
437 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP