1 /*
2 * Copyright (c) 2012, 2020, 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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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 "memory/metaspace.hpp"
31 #include "oops/oopHandle.hpp"
32 #include "oops/weakHandle.hpp"
33 #include "runtime/atomic.hpp"
34 #include "runtime/mutex.hpp"
35 #include "utilities/growableArray.hpp"
36 #include "utilities/macros.hpp"
37 #if INCLUDE_JFR
38 #include "jfr/support/jfrTraceIdExtension.hpp"
39 #endif
40
41 // external name (synthetic) for the primordial "bootstrap" class loader instance
42 #define BOOTSTRAP_LOADER_NAME "bootstrap"
43 #define BOOTSTRAP_LOADER_NAME_LEN 9
44
45 //
46 // A class loader represents a linkset. Conceptually, a linkset identifies
47 // the complete transitive closure of resolved links that a dynamic linker can
48 // produce.
49 //
50 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
51 // used by the dynamic linker to allocate the runtime representation of all
52 // the types it defines.
53 //
54 // ClassLoaderData are stored in the runtime representation of classes,
55 // and provides iterators for root tracing and other GC operations.
56
57 class ClassLoaderDataGraph;
58 class JNIMethodBlock;
59 class ModuleEntry;
60 class PackageEntry;
61 class ModuleEntryTable;
62 class PackageEntryTable;
63 class DictionaryEntry;
64 class Dictionary;
65 class ClassLoaderMetaspace;
66
67 // ClassLoaderData class
68
69 class ClassLoaderData : public CHeapObj<mtClass> {
70 friend class VMStructs;
71
72 private:
73 class ChunkedHandleList {
74 struct Chunk : public CHeapObj<mtClass> {
75 static const size_t CAPACITY = 32;
76
77 oop _data[CAPACITY];
78 volatile juint _size;
79 Chunk* _next;
80
81 Chunk(Chunk* c) : _size(0), _next(c) { }
82 };
83
84 Chunk* volatile _head;
85
86 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
87
88 public:
89 ChunkedHandleList() : _head(NULL) {}
90 ~ChunkedHandleList();
91
92 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
93 // However, multiple threads can execute oops_do concurrently with add.
94 OopHandle add(oop o);
95 bool contains(oop p);
96 NOT_PRODUCT(bool owner_of(oop* p);)
97 void oops_do(OopClosure* f);
98
99 int count() const;
100 };
101
102 friend class ClassLoaderDataGraph;
103 friend class ClassLoaderDataGraphIterator;
104 friend class ClassLoaderDataGraphKlassIteratorAtomic;
105 friend class ClassLoaderDataGraphKlassIteratorStatic;
106 friend class ClassLoaderDataGraphMetaspaceIterator;
107 friend class Klass;
108 friend class MetaDataFactory;
109 friend class Method;
110
111 static ClassLoaderData * _the_null_class_loader_data;
112
113 WeakHandle _holder; // The oop that determines lifetime of this class loader
114 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with
115 // this ClassLoaderData
116
117 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the
118 // classes in the class loader are allocated.
119 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
120 bool _unloading; // true if this class loader goes away
121 bool _has_class_mirror_holder; // If true, CLD is dedicated to one class and that class determines
122 // the CLDs lifecycle. For example, a non-strong hidden class or an
123 // unsafe anonymous class. Arrays of these classes are also assigned
124 // to these class loader datas.
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 int _keep_alive; // if this CLD is kept alive.
131 // Used for non-strong hidden classes, unsafe anonymous classes and the
132 // boot class loader. _keep_alive does not need to be volatile or
133 // atomic since there is one unique CLD per non-strong hidden class
134 // or unsafe anonymous class.
135
136 volatile int _claim; // non-zero if claimed, for example during GC traces.
137 // To avoid applying oop closure more than once.
138 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
139 // have the same life cycle of the corresponding ClassLoader.
140
141 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies
142
143 Klass* volatile _klasses; // The classes defined by the class loader.
144 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
145 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
146 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
147 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
148
149 // These method IDs are created for the class loader and set to NULL when the
150 // class loader is unloaded. They are rarely freed, only for redefine classes
151 // and if they lose a data race in InstanceKlass.
152 JNIMethodBlock* _jmethod_ids;
153
154 // Metadata to be deallocated when it's safe at class unloading, when
155 // this class loader isn't unloaded itself.
156 GrowableArray<Metadata*>* _deallocate_list;
157
158 // Support for walking class loader data objects
159 ClassLoaderData* _next; /// Next loader_datas created
160
161 Klass* _class_loader_klass;
162 Symbol* _name;
163 Symbol* _name_and_id;
164 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
165
166 void set_next(ClassLoaderData* next) { _next = next; }
167 ClassLoaderData* next() const { return Atomic::load(&_next); }
168
169 ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder);
170 ~ClassLoaderData();
171
172 // The CLD are not placed in the Heap, so the Card Table or
173 // the Mod Union Table can't be used to mark when CLD have modified oops.
174 // The CT and MUT bits saves this information for the whole class loader data.
175 void clear_modified_oops() { _modified_oops = false; }
176 public:
177 void record_modified_oops() { _modified_oops = true; }
178 bool has_modified_oops() { return _modified_oops; }
179
180 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
181 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
182 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
183 oop holder_no_keepalive() const;
184 oop holder_phantom() const;
185
186 private:
187 void unload();
188 bool keep_alive() const { return _keep_alive > 0; }
189
190 void classes_do(void f(Klass* const));
191 void loaded_classes_do(KlassClosure* klass_closure);
192 void classes_do(void f(InstanceKlass*));
193 void methods_do(void f(Method*));
194 void modules_do(void f(ModuleEntry*));
195 void packages_do(void f(PackageEntry*));
196
197 // Deallocate free list during class unloading.
198 void free_deallocate_list(); // for the classes that are not unloaded
199 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded
200
201 // Allocate out of this class loader data
202 MetaWord* allocate(size_t size);
203
204 Dictionary* create_dictionary();
205
206 void initialize_name(Handle class_loader);
207
208 public:
209 // GC interface.
210
211 // The "claim" is typically used to check if oops_do needs to be applied on
212 // the CLD or not. Most GCs only perform strong marking during the marking phase.
213 enum Claim {
214 _claim_none = 0,
215 _claim_finalizable = 2,
216 _claim_strong = 3,
217 _claim_other = 4
218 };
219 void clear_claim() { _claim = 0; }
220 void clear_claim(int claim);
221 bool claimed() const { return _claim != 0; }
222 bool claimed(int claim) const { return (_claim & claim) == claim; }
223 bool try_claim(int claim);
224
225 // Computes if the CLD is alive or not. This is safe to call in concurrent
226 // contexts.
227 bool is_alive() const;
228
229 // Accessors
230 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
231
232 static ClassLoaderData* the_null_class_loader_data() {
233 return _the_null_class_loader_data;
234 }
235
236 Mutex* metaspace_lock() const { return _metaspace_lock; }
237
238 bool has_class_mirror_holder() const { return _has_class_mirror_holder; }
239
240 static void init_null_class_loader_data();
241
242 bool is_the_null_class_loader_data() const {
243 return this == _the_null_class_loader_data;
244 }
245
246 // Returns true if this class loader data is for the system class loader.
247 // (Note that the class loader data may be for a non-strong hidden class or unsafe anonymous class)
248 bool is_system_class_loader_data() const;
249
250 // Returns true if this class loader data is for the platform class loader.
251 // (Note that the class loader data may be for a non-strong hidden class or unsafe anonymous class)
252 bool is_platform_class_loader_data() const;
253
254 // Returns true if this class loader data is for the boot class loader.
255 // (Note that the class loader data may be for a non-strong hidden class or unsafe anonymous class)
256 inline bool is_boot_class_loader_data() const;
257
258 bool is_builtin_class_loader_data() const;
259 bool is_permanent_class_loader_data() const;
260
261 // The Metaspace is created lazily so may be NULL. This
262 // method will allocate a Metaspace if needed.
263 ClassLoaderMetaspace* metaspace_non_null();
264
265 inline oop class_loader() const;
266
267 // Returns true if this class loader data is for a loader going away.
268 // Note that this is only safe after the GC has computed if the CLD is
269 // unloading or not. In concurrent contexts where there are no such
270 // guarantees, is_alive() should be used instead.
271 bool is_unloading() const {
272 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
273 return _unloading;
274 }
275
276 // Used to refcount a non-strong hidden class's or unsafe anonymous class's CLD in order to
277 // indicate their aliveness.
278 void inc_keep_alive();
279 void dec_keep_alive();
280
281 void initialize_holder(Handle holder);
282
283 void oops_do(OopClosure* f, int claim_value, bool clear_modified_oops = false);
284
285 void classes_do(KlassClosure* klass_closure);
286 Klass* klasses() { return _klasses; }
287
288 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
289 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
290
291 void print() const;
292 void print_on(outputStream* out) const PRODUCT_RETURN;
293 void print_value() const;
294 void print_value_on(outputStream* out) const;
295 void verify();
296
297 OopHandle add_handle(Handle h);
298 void remove_handle(OopHandle h);
299 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
300 void add_class(Klass* k, bool publicize = true);
301 void remove_class(Klass* k);
302 bool contains_klass(Klass* k);
303 void record_dependency(const Klass* to);
304 PackageEntryTable* packages() { return _packages; }
305 ModuleEntry* unnamed_module() { return _unnamed_module; }
306 ModuleEntryTable* modules();
307 bool modules_defined() { return (_modules != NULL); }
308
309 // Offsets
310 static ByteSize holder_offset() { return in_ByteSize(offset_of(ClassLoaderData, _holder)); }
311 static ByteSize keep_alive_offset() { return in_ByteSize(offset_of(ClassLoaderData, _keep_alive)); }
312
313 // Loaded class dictionary
314 Dictionary* dictionary() const { return _dictionary; }
315
316 void add_to_deallocate_list(Metadata* m);
317
318 static ClassLoaderData* class_loader_data(oop loader);
319 static ClassLoaderData* class_loader_data_or_null(oop 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