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.
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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 "oops/oopHandle.hpp"
30 #include "runtime/handles.hpp"
31 #include "trace/traceMacros.hpp"
32 #include "utilities/growableArray.hpp"
33 #include "utilities/macros.hpp"
34
35 //
36 // A class loader represents a linkset. Conceptually, a linkset identifies
37 // the complete transitive closure of resolved links that a dynamic linker can
38 // produce.
39 //
40 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
41 // used by the dynamic linker to allocate the runtime representation of all
42 // the types it defines.
43 //
44 // ClassLoaderData are stored in the runtime representation of classes,
45 // and provides iterators for root tracing and other GC operations.
46
47 class ClassLoaderData;
48 class Dictionary;
49 class JNIMethodBlock;
50 class Metaspace;
51 class ModuleEntry;
52 class ModuleEntryTable;
53 class Mutex;
54 class PackageEntry;
55 class PackageEntryTable;
56
57 // GC root for walking class loader data created
58
59 class ClassLoaderDataGraph : public AllStatic {
60 friend class ClassLoaderData;
61 friend class ClassLoaderDataGraphKlassIteratorAtomic;
62 friend class ClassLoaderDataGraphKlassIteratorStatic;
63 friend class ClassLoaderDataGraphMetaspaceIterator;
64 friend class VMStructs;
65 private:
66 // All CLDs (except the null CLD) can be reached by walking _head->_next->...
67 static ClassLoaderData* _head;
68 static ClassLoaderData* _unloading;
69 // CMS support.
70 static ClassLoaderData* _saved_head;
71 static ClassLoaderData* _saved_unloading;
72 static bool _should_purge;
73 // OOM has been seen in metaspace allocation. Used to prevent some
74 // allocations until class unloading
75 static bool _metaspace_oom;
76
77 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS);
78 public:
79 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
80 static void purge();
81 static void clear_claimed_marks();
82 // oops do
83 static void oops_do(OopClosure* f, bool must_claim);
84 static void keep_alive_oops_do(OopClosure* blk, bool must_claim);
85 static void always_strong_oops_do(OopClosure* blk, bool must_claim);
86 // cld do
87 static void cld_do(CLDClosure* cl);
88 static void cld_unloading_do(CLDClosure* cl);
89 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
90 static void keep_alive_cld_do(CLDClosure* cl);
91 static void always_strong_cld_do(CLDClosure* cl);
92 // klass do
93 // Walking classes through the ClassLoaderDataGraph include array classes. It also includes
94 // classes that are allocated but not loaded, classes that have errors, and scratch classes
95 // for redefinition. These classes are removed during the next class unloading.
96 // Walking the ClassLoaderDataGraph also includes anonymous classes.
97 static void classes_do(KlassClosure* klass_closure);
98 static void classes_do(void f(Klass* const));
99 static void methods_do(void f(Method*));
100 static void modules_do(void f(ModuleEntry*));
101 static void modules_unloading_do(void f(ModuleEntry*));
102 static void packages_do(void f(PackageEntry*));
103 static void packages_unloading_do(void f(PackageEntry*));
104 static void loaded_classes_do(KlassClosure* klass_closure);
105 static void classes_unloading_do(void f(Klass* const));
106 static bool do_unloading(BoolObjectClosure* is_alive, bool clean_previous_versions);
107
108 // dictionary do
109 // Iterate over all klasses in dictionary, but
110 // just the classes from defining class loaders.
111 static void dictionary_classes_do(void f(InstanceKlass*));
112 // Added for initialize_itable_for_klass to handle exceptions.
113 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS);
114
115 // Iterate all classes and their class loaders, including initiating class loaders.
116 static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*));
117
118 // VM_CounterDecay iteration support
119 static InstanceKlass* try_get_next_class();
120
121 static void verify_dictionary();
122 static void print_dictionary(outputStream* st);
123 static void print_dictionary_statistics(outputStream* st);
124
125 // CMS support.
126 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
127 static GrowableArray<ClassLoaderData*>* new_clds();
128
129 static void set_should_purge(bool b) { _should_purge = b; }
130 static void purge_if_needed() {
131 // Only purge the CLDG for CMS if concurrent sweep is complete.
132 if (_should_purge) {
133 purge();
134 // reset for next time.
135 set_should_purge(false);
136 }
137 }
138
139 static int resize_if_needed();
140
141 static bool has_metaspace_oom() { return _metaspace_oom; }
142 static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
143
144 static void dump_on(outputStream * const out) PRODUCT_RETURN;
145 static bool unload_list_contains(const void* x);
146
147 NOT_PRODUCT(static void verify();)
148 NOT_PRODUCT(static bool contains_loader_data(ClassLoaderData* loader_data);)
149 };
150
151 // ClassLoaderData class
152
153 class ClassLoaderData : public CHeapObj<mtClass> {
154 friend class ClassLoaderDataGraph;
155 friend class ClassLoaderDataGraphKlassIteratorAtomic;
156 friend class ClassLoaderDataGraphKlassIteratorStatic;
157 friend class ClassLoaderDataGraphMetaspaceIterator;
158 friend class MetaDataFactory;
159 friend class Method;
160 friend class Universe;
161 friend class VMStructs;
162 private:
163 class Dependencies VALUE_OBJ_CLASS_SPEC {
164 friend class ClassLoaderData;
165 friend class ClassLoaderDataGraph;
166 private:
167 objArrayOop _list_head;
168 Dependencies() : _list_head(NULL) {}
169 Dependencies(TRAPS) : _list_head(NULL) { init(CHECK); }
170 void init(TRAPS);
171 void add(Handle dependency, TRAPS);
172 void locked_add(objArrayHandle last, objArrayHandle new_dependency, Thread* THREAD);
173 void oops_do(OopClosure* f);
174 };
175
176 class ChunkedHandleList VALUE_OBJ_CLASS_SPEC {
177 friend class ClassLoaderData;
178 private:
179 struct Chunk : public CHeapObj<mtClass> {
180 static const size_t CAPACITY = 32;
181 oop _data[CAPACITY];
182 volatile juint _size;
183 Chunk* _next;
184 Chunk(Chunk* c) : _next(c), _size(0) {}
185 };
186 Chunk* volatile _head;
187 ChunkedHandleList() : _head(NULL) {}
188 ~ChunkedHandleList();
189
190 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
191 // However, multiple threads can execute oops_do concurrently with add.
192 oop* add(oop o);
193 void oops_do(OopClosure* f);
194 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
195 DEBUG_ONLY(bool contains(oop* p);)
196 };
197
198 static ClassLoaderData* _the_null_class_loader_data;
199
200 Dependencies _dependencies; // holds dependencies from this class loader
201 // data to others.
202
203 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
204 // have the same life cycle of the corresponding ClassLoader.
205
206 oop _class_loader; // oop used to uniquely identify a class loader
207 // class loader or a canonical class path
208
209 Metaspace * volatile _metaspace; // Meta-space where meta-data defined by the
210 // classes in the class loader are allocated.
211 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
212
213 Klass* volatile _klasses; // The classes defined by the class loader.
214 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
215 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
216 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
217 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
218
219 // These method IDs are created for the class loader and set to NULL when the
220 // class loader is unloaded. They are rarely freed, only for redefine classes
221 // and if they lose a data race in InstanceKlass.
222 JNIMethodBlock* _jmethod_ids;
223
224 // Metadata to be deallocated when it's safe at class unloading, when
225 // this class loader isn't unloaded itself.
226 GrowableArray<Metadata*>* _deallocate_list;
227
228 // Support for walking class loader data objects
229 ClassLoaderData* _next; /// Next loader_datas created
230
231 s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object().
232 // Used for anonymous classes and the boot class
233 // loader. _keep_alive does not need to be volatile or
234 // atomic since there is one unique CLD per anonymous class.
235
236 volatile int _claimed; // true if claimed, for example during GC traces.
237 // To avoid applying oop closure more than once.
238 // Has to be an int because we cas it.
239
240 TRACE_DEFINE_TRACE_ID_FIELD;
241
242 bool _unloading; // true if this class loader goes away
243 bool _is_anonymous; // if this CLD is for an anonymous class
244
245 // Remembered sets support for the oops in the class loader data.
246 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
247 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
248
249 void set_next(ClassLoaderData* next) { _next = next; }
250 ClassLoaderData* next() const { return _next; }
251
252 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
253 ~ClassLoaderData();
254
255 void init_dependencies(TRAPS);
256
257 // Deallocate free list during class unloading.
258 void free_deallocate_list();
259 void unload_deallocate_list(); // for the classes that are unloaded
260
261 void unload();
262 bool keep_alive() const { return _keep_alive > 0; }
263
264 // The CLD are not placed in the Heap, so the Card Table or
265 // the Mod Union Table can't be used to mark when CLD have modified oops.
266 // The CT and MUT bits saves this information for the whole class loader data.
267 void clear_modified_oops() { _modified_oops = false; }
268
269 void classes_do(void f(Klass*));
270 void classes_do(void f(InstanceKlass*));
271 void loaded_classes_do(KlassClosure* klass_closure);
272 void methods_do(void f(Method*));
273 void modules_do(void f(ModuleEntry*));
274 void packages_do(void f(PackageEntry*));
275
276 public:
277 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
278 void classes_do(KlassClosure* klass_closure);
279
280 void record_modified_oops() { _modified_oops = true; }
281 bool has_modified_oops() const { return _modified_oops; }
282
283 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
284 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
285 bool has_accumulated_modified_oops() const { return _accumulated_modified_oops; }
286
287 bool is_alive(BoolObjectClosure* is_alive_closure) const;
288 // The object the GC is using to keep this ClassLoaderData alive.
289 oop keep_alive_object() const;
290 // Used to refcount an anonymous class's CLD in order to
291 // indicate their aliveness without a keep_alive_object().
292 void inc_keep_alive();
293 void dec_keep_alive();
294
295 // Returns true if this class loader data is for a loader going away.
296 bool is_unloading() const {
297 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
298 return _unloading;
299 }
300
301 void clear_claimed() { _claimed = 0; }
302 bool claimed() const { return _claimed == 1; }
303 bool claim();
304
305 // The Metaspace is created lazily so may be NULL. This
306 // method will allocate a Metaspace if needed.
307 Metaspace* metaspace_non_null();
308 Mutex* metaspace_lock() const { return _metaspace_lock; }
309 Metaspace* metaspace_or_null() const { return _metaspace; }
310
311 bool is_the_null_class_loader_data() const { return this == _the_null_class_loader_data; }
312 bool is_system_class_loader_data() const;
313 bool is_platform_class_loader_data() const;
314 bool is_builtin_class_loader_data() const;
315 bool is_anonymous() const { return _is_anonymous; }
316
317 oop class_loader() const { return _class_loader; }
318 const char* loader_name();
319 unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); }
320 // Loaded class dictionary
321 Dictionary* dictionary() { return _dictionary; }
322
323 Klass* klasses() { return _klasses; }
324 PackageEntryTable* packages() { return _packages; }
325 ModuleEntry* unnamed_module() { return _unnamed_module; }
326 ModuleEntryTable* modules();
327 bool modules_defined() { return (_modules != NULL); }
328
329 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
330 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
331
332 OopHandle add_handle(Handle h);
333 void remove_handle(OopHandle h);
334 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
335 void add_class(Klass* k, bool publicize = true);
336 void remove_class(Klass* k);
337 bool contains_klass(Klass* k);
338 void record_dependency(const Klass* to, TRAPS);
339 void add_to_deallocate_list(Metadata* m);
340
341 TRACE_DEFINE_TRACE_ID_METHODS;
342
343 void print() { print_on(tty); }
344 void print_on(outputStream* out) const;
345 void print_value() { print_value_on(tty); }
346 void print_value_on(outputStream* out) const;
347 void dump(outputStream * const out) PRODUCT_RETURN;
348 NOT_PRODUCT(void verify();)
349
350 static void init_null_class_loader_data();
351 static ClassLoaderData* the_null_class_loader_data() { return _the_null_class_loader_data; }
352 static ClassLoaderData* class_loader_data(oop loader);
353 static ClassLoaderData* class_loader_data_or_null(oop loader);
354 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
355 };
356
357 // An iterator that distributes Klasses to parallel worker threads.
358 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
359 private:
360 Klass* volatile _next_klass;
361 public:
362 ClassLoaderDataGraphKlassIteratorAtomic();
363 Klass* next_klass();
364 static Klass* next_klass_in_cldg(Klass* klass);
365 };
366
367 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
368 private:
369 ClassLoaderData* _data;
370 public:
371 ClassLoaderDataGraphMetaspaceIterator();
372 bool repeat() { return _data != NULL; }
373 Metaspace* get_next() {
374 assert(_data != NULL, "Should not be NULL in call to the iterator");
375 Metaspace* result = _data->metaspace_or_null();
376 _data = _data->next();
377 // This result might be NULL for class loaders without metaspace
378 // yet. It would be nice to return only non-null results but
379 // there is no guarantee that there will be a non-null result
380 // down the list so the caller is going to have to check.
381 return result;
382 }
383 };
384
385 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP