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.
22 *
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/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 // ClassLoaderData class
66
67 class ClassLoaderData : public CHeapObj<mtClass> {
68 friend class VMStructs;
69
70 private:
71 class ChunkedHandleList {
72 struct Chunk : public CHeapObj<mtClass> {
73 static const size_t CAPACITY = 32;
74
75 oop _data[CAPACITY];
76 volatile juint _size;
77 Chunk* _next;
78
79 Chunk(Chunk* c) : _size(0), _next(c) { }
80 };
81
82 Chunk* volatile _head;
83
84 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
85
86 public:
87 ChunkedHandleList() : _head(NULL) {}
88 ~ChunkedHandleList();
89
90 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
91 // However, multiple threads can execute oops_do concurrently with add.
92 oop* add(oop o);
93 bool contains(oop p);
94 NOT_PRODUCT(bool owner_of(oop* p);)
95 void oops_do(OopClosure* f);
96
97 int count() const;
98 };
99
100 friend class ClassLoaderDataGraph;
101 friend class ClassLoaderDataGraphIterator;
102 friend class ClassLoaderDataGraphKlassIteratorAtomic;
103 friend class ClassLoaderDataGraphKlassIteratorStatic;
104 friend class ClassLoaderDataGraphMetaspaceIterator;
105 friend class Klass;
106 friend class MetaDataFactory;
107 friend class Method;
108
109 static ClassLoaderData * _the_null_class_loader_data;
110
111 WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader
112 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with
113 // this ClassLoaderData
114
115 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the
116 // classes in the class loader are allocated.
117 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
118 bool _unloading; // true if this class loader goes away
119 bool _is_unsafe_anonymous; // CLD is dedicated to one class and that class determines the CLDs lifecycle.
120 // For example, an unsafe anonymous class.
121
122 // Remembered sets support for the oops in the class loader data.
123 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
124 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
125
126 s2 _keep_alive; // if this CLD is kept alive.
127 // Used for unsafe anonymous classes and the boot class
128 // loader. _keep_alive does not need to be volatile or
129 // atomic since there is one unique CLD per unsafe anonymous class.
130
131 volatile int _claim; // non-zero if claimed, for example during GC traces.
132 // To avoid applying oop closure more than once.
133 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
134 // have the same life cycle of the corresponding ClassLoader.
135
136 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies
137
138 Klass* volatile _klasses; // The classes defined by the class loader.
139 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
140 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
141 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
142 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
143
144 // These method IDs are created for the class loader and set to NULL when the
145 // class loader is unloaded. They are rarely freed, only for redefine classes
146 // and if they lose a data race in InstanceKlass.
147 JNIMethodBlock* _jmethod_ids;
148
149 // Metadata to be deallocated when it's safe at class unloading, when
150 // this class loader isn't unloaded itself.
151 GrowableArray<Metadata*>* _deallocate_list;
152
153 // Support for walking class loader data objects
154 ClassLoaderData* _next; /// Next loader_datas created
155
156 Klass* _class_loader_klass;
157 Symbol* _name;
158 Symbol* _name_and_id;
159 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
160
161 void set_next(ClassLoaderData* next) { _next = next; }
162 ClassLoaderData* next() const { return _next; }
163
164 ClassLoaderData(Handle h_class_loader, bool is_unsafe_anonymous);
165 ~ClassLoaderData();
166
167 // The CLD are not placed in the Heap, so the Card Table or
168 // the Mod Union Table can't be used to mark when CLD have modified oops.
169 // The CT and MUT bits saves this information for the whole class loader data.
170 void clear_modified_oops() { _modified_oops = false; }
171 public:
172 void record_modified_oops() { _modified_oops = true; }
173 bool has_modified_oops() { return _modified_oops; }
174
175 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
176 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
177 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
178 oop holder_no_keepalive() const;
179 oop holder_phantom() const;
180
181 private:
182 void unload();
183 bool keep_alive() const { return _keep_alive > 0; }
184
185 void classes_do(void f(Klass* const));
186 void loaded_classes_do(KlassClosure* klass_closure);
187 void classes_do(void f(InstanceKlass*));
188 void value_classes_do(void f(ValueKlass*));
189 void methods_do(void f(Method*));
190 void modules_do(void f(ModuleEntry*));
191 void packages_do(void f(PackageEntry*));
192
193 // Deallocate free list during class unloading.
194 void free_deallocate_list(); // for the classes that are not unloaded
195 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded
196
197 // Allocate out of this class loader data
198 MetaWord* allocate(size_t size);
199
200 Dictionary* create_dictionary();
201
202 void initialize_name(Handle class_loader);
203
204 public:
205 // GC interface.
206
207 // The "claim" is typically used to check if oops_do needs to be applied on
208 // the CLD or not. Most GCs only perform strong marking during the marking phase.
209 enum {
210 _claim_none = 0,
211 _claim_finalizable = 2,
212 _claim_strong = 3
213 };
214 void clear_claim() { _claim = 0; }
215 bool claimed() const { return _claim != 0; }
216 bool try_claim(int claim);
217 int get_claim() const { return _claim; }
218 void set_claim(int claim) { _claim = claim; }
219
220 // Computes if the CLD is alive or not. This is safe to call in concurrent
221 // contexts.
222 bool is_alive() const;
223
224 // Accessors
225 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
226
227 static ClassLoaderData* the_null_class_loader_data() {
228 return _the_null_class_loader_data;
229 }
230
231 Mutex* metaspace_lock() const { return _metaspace_lock; }
232
233 bool is_unsafe_anonymous() const { return _is_unsafe_anonymous; }
234
235 static void init_null_class_loader_data();
236
237 bool is_the_null_class_loader_data() const {
238 return this == _the_null_class_loader_data;
239 }
240
241 // Returns true if this class loader data is for the system class loader.
242 // (Note that the class loader data may be unsafe anonymous.)
243 bool is_system_class_loader_data() const;
244
245 // Returns true if this class loader data is for the platform class loader.
246 // (Note that the class loader data may be unsafe anonymous.)
247 bool is_platform_class_loader_data() const;
248
249 // Returns true if this class loader data is for the boot class loader.
250 // (Note that the class loader data may be unsafe anonymous.)
251 inline bool is_boot_class_loader_data() const;
252
253 bool is_builtin_class_loader_data() const;
254 bool is_permanent_class_loader_data() const;
255
256 // The Metaspace is created lazily so may be NULL. This
257 // method will allocate a Metaspace if needed.
258 ClassLoaderMetaspace* metaspace_non_null();
259
260 inline oop class_loader() const;
261
262 // Returns true if this class loader data is for a loader going away.
263 // Note that this is only safe after the GC has computed if the CLD is
264 // unloading or not. In concurrent contexts where there are no such
265 // guarantees, is_alive() should be used instead.
266 bool is_unloading() const {
267 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
268 return _unloading;
269 }
270
271 // Used to refcount an unsafe anonymous class's CLD in order to
272 // indicate their aliveness.
273 void inc_keep_alive();
274 void dec_keep_alive();
275
276 void initialize_holder(Handle holder);
277
278 void oops_do(OopClosure* f, int claim_value, bool clear_modified_oops = false);
279
280 void classes_do(KlassClosure* klass_closure);
281 Klass* klasses() { return _klasses; }
282
283 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
284 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
285
286 void print() { print_on(tty); }
287 void print_on(outputStream* out) const PRODUCT_RETURN;
288 void print_value() { print_value_on(tty); }
289 void print_value_on(outputStream* out) const;
290 void verify();
291
292 OopHandle add_handle(Handle h);
293 void remove_handle(OopHandle h);
294 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
295 void add_class(Klass* k, bool publicize = true);
296 void remove_class(Klass* k);
297 bool contains_klass(Klass* k);
298 void record_dependency(const Klass* to);
299 PackageEntryTable* packages() { return _packages; }
300 ModuleEntry* unnamed_module() { return _unnamed_module; }
301 ModuleEntryTable* modules();
302 bool modules_defined() { return (_modules != NULL); }
303
304 // Loaded class dictionary
305 Dictionary* dictionary() const { return _dictionary; }
306
307 void add_to_deallocate_list(Metadata* m);
308
309 static ClassLoaderData* class_loader_data(oop loader);
310 static ClassLoaderData* class_loader_data_or_null(oop loader);
311 static ClassLoaderData* unsafe_anonymous_class_loader_data(Handle loader);
312
313 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'.
314 // Also works if unloading.
315 Klass* class_loader_klass() const { return _class_loader_klass; }
316
317 // Returns the class loader's explict name as specified during
318 // construction or the class loader's qualified class name.
319 // Works during unloading.
320 const char* loader_name() const;
321 // Returns the explicitly specified class loader name or NULL.
322 Symbol* name() const { return _name; }
323
324 // Obtain the class loader's _name_and_id, works during unloading.
325 const char* loader_name_and_id() const;
326 Symbol* name_and_id() const { return _name_and_id; }
327
328 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
329 };
330
331 #endif // SHARE_CLASSFILE_CLASSLOADERDATA_HPP