1 /*
2 * Copyright (c) 2012, 2019, 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_CLASSFILE_CLASSLOADERDATA_HPP
26 #define SHARE_CLASSFILE_CLASSLOADERDATA_HPP
27
28 #include "memory/allocation.hpp"
29 #include "memory/memRegion.hpp"
30 #include "oops/oopHandle.hpp"
31 #include "oops/weakHandle.hpp"
32 #include "runtime/atomic.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 ClassLoaderDataGraph;
57 class JNIMethodBlock;
58 class ModuleEntry;
59 class PackageEntry;
60 class ModuleEntryTable;
61 class PackageEntryTable;
62 class DictionaryEntry;
63 class Dictionary;
64
65 namespace metaspace {
66 class ClassLoaderMetaspace;
67 }
68
69 // ClassLoaderData class
70
71 class ClassLoaderData : public CHeapObj<mtClass> {
72 friend class VMStructs;
73
74 private:
75 class ChunkedHandleList {
76 struct Chunk : public CHeapObj<mtClass> {
77 static const size_t CAPACITY = 32;
78
79 oop _data[CAPACITY];
80 volatile juint _size;
81 Chunk* _next;
82
83 Chunk(Chunk* c) : _size(0), _next(c) { }
84 };
85
86 Chunk* volatile _head;
87
88 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
89
90 public:
91 ChunkedHandleList() : _head(NULL) {}
92 ~ChunkedHandleList();
93
94 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
95 // However, multiple threads can execute oops_do concurrently with add.
96 oop* add(oop o);
97 bool contains(oop p);
98 NOT_PRODUCT(bool owner_of(oop* p);)
99 void oops_do(OopClosure* f);
100
101 int count() const;
102 };
103
104 friend class ClassLoaderDataGraph;
105 friend class ClassLoaderDataGraphIterator;
106 friend class ClassLoaderDataGraphKlassIteratorAtomic;
107 friend class ClassLoaderDataGraphKlassIteratorStatic;
108 friend class ClassLoaderDataGraphMetaspaceIterator;
109 friend class Klass;
110 friend class MetaDataFactory;
111 friend class Method;
112
113 static ClassLoaderData * _the_null_class_loader_data;
114
115 WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader
116 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with
117 // this ClassLoaderData
118
119 metaspace::ClassLoaderMetaspace* volatile _metaspace; // Meta-space where meta-data defined by the
120 // classes in the class loader are allocated.
121 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
122 bool _unloading; // true if this class loader goes away
123 bool _is_unsafe_anonymous; // CLD is dedicated to one class and that class determines the CLDs lifecycle.
124 // For example, an unsafe anonymous class.
125
126 // Remembered sets support for the oops in the class loader data.
127 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
128 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
129
130 s2 _keep_alive; // if this CLD is kept alive.
131 // Used for unsafe anonymous classes and the boot class
132 // loader. _keep_alive does not need to be volatile or
133 // atomic since there is one unique CLD per unsafe anonymous class.
134
135 volatile int _claim; // non-zero if claimed, for example during GC traces.
136 // To avoid applying oop closure more than once.
137 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
138 // have the same life cycle of the corresponding ClassLoader.
139
140 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies
141
142 Klass* volatile _klasses; // The classes defined by the class loader.
143 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
144 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
145 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
146 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
147
148 // These method IDs are created for the class loader and set to NULL when the
149 // class loader is unloaded. They are rarely freed, only for redefine classes
150 // and if they lose a data race in InstanceKlass.
151 JNIMethodBlock* _jmethod_ids;
152
153 // Metadata to be deallocated when it's safe at class unloading, when
154 // this class loader isn't unloaded itself.
155 GrowableArray<Metadata*>* _deallocate_list;
156
157 // Support for walking class loader data objects
158 ClassLoaderData* _next; /// Next loader_datas created
159
160 Klass* _class_loader_klass;
161 Symbol* _name;
162 Symbol* _name_and_id;
163 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
164
165 void set_next(ClassLoaderData* next) { _next = next; }
166 ClassLoaderData* next() const { return Atomic::load(&_next); }
167
168 ClassLoaderData(Handle h_class_loader, bool is_unsafe_anonymous);
169 ~ClassLoaderData();
170
171 // The CLD are not placed in the Heap, so the Card Table or
172 // the Mod Union Table can't be used to mark when CLD have modified oops.
173 // The CT and MUT bits saves this information for the whole class loader data.
174 void clear_modified_oops() { _modified_oops = false; }
175 public:
176 void record_modified_oops() { _modified_oops = true; }
177 bool has_modified_oops() { return _modified_oops; }
178
179 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
180 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
181 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
182 oop holder_no_keepalive() const;
183 oop holder_phantom() const;
184
185 private:
186 void unload();
187 bool keep_alive() const { return _keep_alive > 0; }
188
189 void classes_do(void f(Klass* const));
190 void loaded_classes_do(KlassClosure* klass_closure);
191 void classes_do(void f(InstanceKlass*));
192 void methods_do(void f(Method*));
193 void modules_do(void f(ModuleEntry*));
194 void packages_do(void f(PackageEntry*));
195
196 // Deallocate free list during class unloading.
197 void free_deallocate_list(); // for the classes that are not unloaded
198 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded
199
200 // Allocate out of this class loader data
201 MetaWord* allocate(size_t size);
202
203 Dictionary* create_dictionary();
204
205 void initialize_name(Handle class_loader);
206
207 public:
208 // GC interface.
209
210 // The "claim" is typically used to check if oops_do needs to be applied on
211 // the CLD or not. Most GCs only perform strong marking during the marking phase.
212 enum Claim {
213 _claim_none = 0,
214 _claim_finalizable = 2,
215 _claim_strong = 3,
216 _claim_other = 4
217 };
218 void clear_claim() { _claim = 0; }
219 void clear_claim(int claim);
220 bool claimed() const { return _claim != 0; }
221 bool claimed(int claim) const { return (_claim & claim) == claim; }
222 bool try_claim(int claim);
223
224 // Computes if the CLD is alive or not. This is safe to call in concurrent
225 // contexts.
226 bool is_alive() const;
227
228 // Accessors
229 metaspace::ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
230
231 static ClassLoaderData* the_null_class_loader_data() {
232 return _the_null_class_loader_data;
233 }
234
235 Mutex* metaspace_lock() const { return _metaspace_lock; }
236
237 bool is_unsafe_anonymous() const { return _is_unsafe_anonymous; }
238
239 static void init_null_class_loader_data();
240
241 bool is_the_null_class_loader_data() const {
242 return this == _the_null_class_loader_data;
243 }
244
245 // Returns true if this class loader data is for the system class loader.
246 // (Note that the class loader data may be unsafe anonymous.)
247 bool is_system_class_loader_data() const;
248
249 // Returns true if this class loader data is for the platform class loader.
250 // (Note that the class loader data may be unsafe anonymous.)
251 bool is_platform_class_loader_data() const;
252
253 // Returns true if this class loader data is for the boot class loader.
254 // (Note that the class loader data may be unsafe anonymous.)
255 inline bool is_boot_class_loader_data() const;
256
257 bool is_builtin_class_loader_data() const;
258 bool is_permanent_class_loader_data() const;
259
260 // The Metaspace is created lazily so may be NULL. This
261 // method will allocate a Metaspace if needed.
262 metaspace::ClassLoaderMetaspace* metaspace_non_null();
263
264 inline oop class_loader() const;
265
266 // Returns true if this class loader data is for a loader going away.
267 // Note that this is only safe after the GC has computed if the CLD is
268 // unloading or not. In concurrent contexts where there are no such
269 // guarantees, is_alive() should be used instead.
270 bool is_unloading() const {
271 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
272 return _unloading;
273 }
274
275 // Used to refcount an unsafe anonymous class's CLD in order to
276 // indicate their aliveness.
277 void inc_keep_alive();
278 void dec_keep_alive();
279
280 void initialize_holder(Handle holder);
281
282 void oops_do(OopClosure* f, int claim_value, bool clear_modified_oops = false);
283
284 void classes_do(KlassClosure* klass_closure);
285 Klass* klasses() { return _klasses; }
286
287 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
288 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
289
290 void print() const;
291 void print_on(outputStream* out) const PRODUCT_RETURN;
292 void print_value() const;
293 void print_value_on(outputStream* out) const;
294 void verify();
295
296 OopHandle add_handle(Handle h);
297 void remove_handle(OopHandle h);
298 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
299 void add_class(Klass* k, bool publicize = true);
300 void remove_class(Klass* k);
301 bool contains_klass(Klass* k);
302 void record_dependency(const Klass* to);
303 PackageEntryTable* packages() { return _packages; }
304 ModuleEntry* unnamed_module() { return _unnamed_module; }
305 ModuleEntryTable* modules();
306 bool modules_defined() { return (_modules != NULL); }
307
308 // Offsets
309 static ByteSize holder_offset() { return in_ByteSize(offset_of(ClassLoaderData, _holder)); }
310 static ByteSize keep_alive_offset() { return in_ByteSize(offset_of(ClassLoaderData, _keep_alive)); }
311
312 // Loaded class dictionary
313 Dictionary* dictionary() const { return _dictionary; }
314
315 void add_to_deallocate_list(Metadata* m);
316
317 static ClassLoaderData* class_loader_data(oop loader);
318 static ClassLoaderData* class_loader_data_or_null(oop loader);
319 static ClassLoaderData* unsafe_anonymous_class_loader_data(Handle loader);
320
321 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'.
322 // Also works if unloading.
323 Klass* class_loader_klass() const { return _class_loader_klass; }
324
325 // Returns the class loader's explict name as specified during
326 // construction or the class loader's qualified class name.
327 // Works during unloading.
328 const char* loader_name() const;
329 // Returns the explicitly specified class loader name or NULL.
330 Symbol* name() const { return _name; }
331
332 // Obtain the class loader's _name_and_id, works during unloading.
333 const char* loader_name_and_id() const;
334 Symbol* name_and_id() const { return _name_and_id; }
335
336 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
337 };
338
339 #endif // SHARE_CLASSFILE_CLASSLOADERDATA_HPP