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