1 /*
2 * Copyright (c) 1997, 2015, 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
20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25 #ifndef SHARE_VM_RUNTIME_HANDLES_HPP
26 #define SHARE_VM_RUNTIME_HANDLES_HPP
27
28 #include "gc/shared/barrierSet.hpp"
29 #include "oops/oop.hpp"
30 #include "oops/oopsHierarchy.hpp"
31
32 class InstanceKlass;
33 class Klass;
34
35 //------------------------------------------------------------------------------------------------------------------------
36 // In order to preserve oops during garbage collection, they should be
37 // allocated and passed around via Handles within the VM. A handle is
38 // simply an extra indirection allocated in a thread local handle area.
39 //
40 // A handle is a ValueObj, so it can be passed around as a value, can
41 // be used as a parameter w/o using &-passing, and can be returned as a
42 // return value.
43 //
44 // oop parameters and return types should be Handles whenever feasible.
45 //
46 // Handles are declared in a straight-forward manner, e.g.
47 //
48 // oop obj = ...;
49 // Handle h1(obj); // allocate new handle
50 // Handle h2(thread, obj); // faster allocation when current thread is known
51 // Handle h3; // declare handle only, no allocation occurs
52 // ...
53 // h3 = h1; // make h3 refer to same indirection as h1
54 // oop obj2 = h2(); // get handle value
55 // h1->print(); // invoking operation on oop
56 //
57 // Handles are specialized for different oop types to provide extra type
58 // information and avoid unnecessary casting. For each oop type xxxOop
59 // there is a corresponding handle called xxxHandle, e.g.
60 //
61 // oop Handle
62 // Method* methodHandle
63 // instanceOop instanceHandle
64
65 //------------------------------------------------------------------------------------------------------------------------
66 // Base class for all handles. Provides overloading of frequently
67 // used operators for ease of use.
68
69 class Handle VALUE_OBJ_CLASS_SPEC {
70 private:
71 oop* _handle;
72
73 protected:
74 oop obj() const { return _handle == NULL ? (oop)NULL : *_handle; }
75 oop non_null_obj() const { assert(_handle != NULL, "resolving NULL handle"); return *_handle; }
76
77 public:
78 // Constructors
79 Handle() { _handle = NULL; }
80 Handle(oop obj);
81 Handle(Thread* thread, oop obj);
82
83 // General access
84 oop operator () () const { return obj(); }
85 oop operator -> () const { return non_null_obj(); }
86 bool operator == (oop o) const { return oopDesc::bs()->write_barrier(obj()) == oopDesc::bs()->write_barrier(o); }
87 bool operator == (const Handle& h) const { return oopDesc::bs()->write_barrier(obj()) == oopDesc::bs()->write_barrier(h.obj()); }
88
89 // Null checks
90 bool is_null() const { return _handle == NULL; }
91 bool not_null() const { return _handle != NULL; }
92
93 // Debugging
94 void print() { obj()->print(); }
95
96 // Direct interface, use very sparingly.
97 // Used by JavaCalls to quickly convert handles and to create handles static data structures.
98 // Constructor takes a dummy argument to prevent unintentional type conversion in C++.
99 Handle(oop *handle, bool dummy) { _handle = handle; }
100
101 // Raw handle access. Allows easy duplication of Handles. This can be very unsafe
102 // since duplicates is only valid as long as original handle is alive.
103 oop* raw_value() { return _handle; }
104 static oop raw_resolve(oop *handle) { return handle == NULL ? (oop)NULL : *handle; }
105 };
106
107 // Specific Handles for different oop types
108 #define DEF_HANDLE(type, is_a) \
109 class type##Handle: public Handle { \
110 protected: \
111 type##Oop obj() const { return (type##Oop)Handle::obj(); } \
112 type##Oop non_null_obj() const { return (type##Oop)Handle::non_null_obj(); } \
113 \
114 public: \
115 /* Constructors */ \
116 type##Handle () : Handle() {} \
117 type##Handle (type##Oop obj) : Handle((oop)obj) { \
118 assert(is_null() || ((oop)obj)->is_a(), \
119 "illegal type"); \
120 } \
121 type##Handle (Thread* thread, type##Oop obj) : Handle(thread, (oop)obj) { \
122 assert(is_null() || ((oop)obj)->is_a(), "illegal type"); \
123 } \
124 \
125 /* Operators for ease of use */ \
126 type##Oop operator () () const { return obj(); } \
127 type##Oop operator -> () const { return non_null_obj(); } \
128 };
129
130
131 DEF_HANDLE(instance , is_instance_noinline )
132 DEF_HANDLE(array , is_array_noinline )
133 DEF_HANDLE(objArray , is_objArray_noinline )
134 DEF_HANDLE(typeArray , is_typeArray_noinline )
135
136 //------------------------------------------------------------------------------------------------------------------------
137
138 // Metadata Handles. Unlike oop Handles these are needed to prevent metadata
139 // from being reclaimed by RedefineClasses.
140
141 // Specific Handles for different oop types
142 #define DEF_METADATA_HANDLE(name, type) \
143 class name##Handle; \
144 class name##Handle : public StackObj { \
145 type* _value; \
146 Thread* _thread; \
147 protected: \
148 type* obj() const { return _value; } \
149 type* non_null_obj() const { assert(_value != NULL, "resolving NULL _value"); return _value; } \
150 \
151 public: \
152 /* Constructors */ \
153 name##Handle () : _value(NULL), _thread(NULL) {} \
154 name##Handle (type* obj); \
155 name##Handle (Thread* thread, type* obj); \
156 \
157 name##Handle (const name##Handle &h); \
158 name##Handle& operator=(const name##Handle &s); \
159 \
160 /* Destructor */ \
161 ~name##Handle (); \
162 void remove(); \
163 \
164 /* Operators for ease of use */ \
165 type* operator () () const { return obj(); } \
166 type* operator -> () const { return non_null_obj(); } \
167 \
168 bool operator == (type* o) const { return obj() == o; } \
169 bool operator == (const name##Handle& h) const { return obj() == h.obj(); } \
170 \
171 /* Null checks */ \
172 bool is_null() const { return _value == NULL; } \
173 bool not_null() const { return _value != NULL; } \
174 };
175
176
177 DEF_METADATA_HANDLE(method, Method)
178 DEF_METADATA_HANDLE(constantPool, ConstantPool)
179
180 // Writing this class explicitly, since DEF_METADATA_HANDLE(klass) doesn't
181 // provide the necessary Klass* <-> Klass* conversions. This Klass
182 // could be removed when we don't have the Klass* typedef anymore.
183 class KlassHandle : public StackObj {
184 Klass* _value;
185 protected:
186 Klass* obj() const { return _value; }
187 Klass* non_null_obj() const { assert(_value != NULL, "resolving NULL _value"); return _value; }
188
189 public:
190 KlassHandle() : _value(NULL) {}
191 KlassHandle(const Klass* obj) : _value(const_cast<Klass *>(obj)) {};
192 KlassHandle(Thread* thread, const Klass* obj) : _value(const_cast<Klass *>(obj)) {};
193
194 Klass* operator () () const { return obj(); }
195 Klass* operator -> () const { return non_null_obj(); }
196
197 bool operator == (Klass* o) const { return obj() == o; }
198 bool operator == (const KlassHandle& h) const { return obj() == h.obj(); }
199
200 bool is_null() const { return _value == NULL; }
201 bool not_null() const { return _value != NULL; }
202 };
203
204 class instanceKlassHandle : public KlassHandle {
205 public:
206 /* Constructors */
207 instanceKlassHandle () : KlassHandle() {}
208 instanceKlassHandle (const Klass* k) : KlassHandle(k) {
209 assert(k == NULL || is_instanceKlass(k), "illegal type");
210 }
211 instanceKlassHandle (Thread* thread, const Klass* k) : KlassHandle(thread, k) {
212 assert(k == NULL || is_instanceKlass(k), "illegal type");
213 }
214 /* Access to klass part */
215 InstanceKlass* operator () () const { return (InstanceKlass*)obj(); }
216 InstanceKlass* operator -> () const { return (InstanceKlass*)obj(); }
217
218 debug_only(bool is_instanceKlass(const Klass* k));
219 };
220
221
222 //------------------------------------------------------------------------------------------------------------------------
223 // Thread local handle area
224 class HandleArea: public Arena {
225 friend class HandleMark;
226 friend class NoHandleMark;
227 friend class ResetNoHandleMark;
228 #ifdef ASSERT
229 int _handle_mark_nesting;
230 int _no_handle_mark_nesting;
231 #endif
232 HandleArea* _prev; // link to outer (older) area
233 public:
234 // Constructor
235 HandleArea(HandleArea* prev) : Arena(mtThread, Chunk::tiny_size) {
236 debug_only(_handle_mark_nesting = 0);
237 debug_only(_no_handle_mark_nesting = 0);
238 _prev = prev;
239 }
240
241 // Handle allocation
242 private:
243 oop* real_allocate_handle(oop obj) {
244 #ifdef ASSERT
245 oop* handle = (oop*) (UseMallocOnly ? internal_malloc_4(oopSize) : Amalloc_4(oopSize));
246 #else
247 oop* handle = (oop*) Amalloc_4(oopSize);
248 #endif
249 *handle = obj;
250 return handle;
251 }
252 public:
253 #ifdef ASSERT
254 oop* allocate_handle(oop obj);
255 #else
256 oop* allocate_handle(oop obj) { return real_allocate_handle(obj); }
257 #endif
258
259 // Garbage collection support
260 void oops_do(OopClosure* f);
261
262 // Number of handles in use
263 size_t used() const { return Arena::used() / oopSize; }
264
265 debug_only(bool no_handle_mark_active() { return _no_handle_mark_nesting > 0; })
266 };
267
268
269 //------------------------------------------------------------------------------------------------------------------------
270 // Handles are allocated in a (growable) thread local handle area. Deallocation
271 // is managed using a HandleMark. It should normally not be necessary to use
272 // HandleMarks manually.
273 //
274 // A HandleMark constructor will record the current handle area top, and the
275 // destructor will reset the top, destroying all handles allocated in between.
276 // The following code will therefore NOT work:
277 //
278 // Handle h;
279 // {
280 // HandleMark hm;
281 // h = Handle(obj);
282 // }
283 // h()->print(); // WRONG, h destroyed by HandleMark destructor.
284 //
285 // If h has to be preserved, it can be converted to an oop or a local JNI handle
286 // across the HandleMark boundary.
287
288 // The base class of HandleMark should have been StackObj but we also heap allocate
289 // a HandleMark when a thread is created. The operator new is for this special case.
290
291 class HandleMark {
292 private:
293 Thread *_thread; // thread that owns this mark
294 HandleArea *_area; // saved handle area
295 Chunk *_chunk; // saved arena chunk
296 char *_hwm, *_max; // saved arena info
297 size_t _size_in_bytes; // size of handle area
298 // Link to previous active HandleMark in thread
299 HandleMark* _previous_handle_mark;
300
301 void initialize(Thread* thread); // common code for constructors
302 void set_previous_handle_mark(HandleMark* mark) { _previous_handle_mark = mark; }
303 HandleMark* previous_handle_mark() const { return _previous_handle_mark; }
304
305 size_t size_in_bytes() const { return _size_in_bytes; }
306 public:
307 HandleMark(); // see handles_inline.hpp
308 HandleMark(Thread* thread) { initialize(thread); }
309 ~HandleMark();
310
311 // Functions used by HandleMarkCleaner
312 // called in the constructor of HandleMarkCleaner
313 void push();
314 // called in the destructor of HandleMarkCleaner
315 void pop_and_restore();
316 // overloaded operators
317 void* operator new(size_t size) throw();
318 void* operator new [](size_t size) throw();
319 void operator delete(void* p);
320 void operator delete[](void* p);
321 };
322
323 //------------------------------------------------------------------------------------------------------------------------
324 // A NoHandleMark stack object will verify that no handles are allocated
325 // in its scope. Enabled in debug mode only.
326
327 class NoHandleMark: public StackObj {
328 public:
329 #ifdef ASSERT
330 NoHandleMark();
331 ~NoHandleMark();
332 #else
333 NoHandleMark() {}
334 ~NoHandleMark() {}
335 #endif
336 };
337
338
339 class ResetNoHandleMark: public StackObj {
340 int _no_handle_mark_nesting;
341 public:
342 #ifdef ASSERT
343 ResetNoHandleMark();
344 ~ResetNoHandleMark();
345 #else
346 ResetNoHandleMark() {}
347 ~ResetNoHandleMark() {}
348 #endif
349 };
350
351 #endif // SHARE_VM_RUNTIME_HANDLES_HPP