1 /*
2 * Copyright (c) 2003, 2021, 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
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23 */
24
25 #ifndef SHARE_CLASSFILE_PLACEHOLDERS_HPP
26 #define SHARE_CLASSFILE_PLACEHOLDERS_HPP
27
28 #include "utilities/hashtable.hpp"
29
30 class PlaceholderEntry;
31 class Thread;
32 class ClassLoaderData;
33 class Symbol;
34
35 // Placeholder objects. These represent classes currently
36 // being loaded, as well as arrays of primitives.
37 //
38
39 class PlaceholderTable : public Hashtable<Symbol*, mtClass> {
40
41 public:
42 PlaceholderTable(int table_size);
43
44 PlaceholderEntry* new_entry(int hash, Symbol* name, ClassLoaderData* loader_data, Symbol* supername);
45 void free_entry(PlaceholderEntry* entry);
46
47 PlaceholderEntry* bucket(int i) const {
48 return (PlaceholderEntry*)Hashtable<Symbol*, mtClass>::bucket(i);
49 }
50
51 PlaceholderEntry** bucket_addr(int i) {
52 return (PlaceholderEntry**)Hashtable<Symbol*, mtClass>::bucket_addr(i);
53 }
54
55 PlaceholderEntry* add_entry(unsigned int hash, Symbol* name,
56 ClassLoaderData* loader_data,
57 Symbol* supername);
58
59 // This returns a Symbol* to match type for SystemDictionary
60 Symbol* find_entry(unsigned int hash,
61 Symbol* name, ClassLoaderData* loader_data);
62
63 PlaceholderEntry* get_entry(unsigned int hash,
64 Symbol* name, ClassLoaderData* loader_data);
65
66 // caller to create a placeholder entry must enumerate an action
67 // caller claims ownership of that action
68 // For parallel classloading:
69 // multiple LOAD_INSTANCE threads can proceed in parallel
70 // multiple LOAD_SUPER threads can proceed in parallel
71 // LOAD_SUPER needed to check for class circularity
72 // DEFINE_CLASS: ultimately define class must be single threaded
73 // on a class/classloader basis
74 // so the head of that queue owns the token
75 // and the rest of the threads return the result the first thread gets
76 // PRIMITIVE_OBJECT_FIELD: needed to check for inline type fields circularity
77 enum classloadAction {
78 LOAD_INSTANCE = 1, // calling load_instance_class
79 LOAD_SUPER = 2, // loading superclass for this class
80 DEFINE_CLASS = 3, // find_or_define class
81 PRIMITIVE_OBJECT_FIELD = 4 // primitive object fields
82 };
83
84 // find_and_add returns probe pointer - old or new
85 // If no entry exists, add a placeholder entry and push SeenThread for classloadAction
86 // If entry exists, reuse entry and push SeenThread for classloadAction
87 PlaceholderEntry* find_and_add(unsigned int hash,
88 Symbol* name, ClassLoaderData* loader_data,
89 classloadAction action, Symbol* supername,
90 JavaThread* thread);
91
92 void remove_entry(unsigned int hash,
93 Symbol* name, ClassLoaderData* loader_data);
94
95 // find_and_remove first removes SeenThread for classloadAction
96 // If all queues are empty and definer is null, remove the PlacheholderEntry completely
97 void find_and_remove(unsigned int hash,
98 Symbol* name, ClassLoaderData* loader_data,
99 classloadAction action, JavaThread* thread);
100
101 void print_on(outputStream* st) const;
102 void print() const;
103 void verify();
104 };
105
106 class SeenThread;
107
108 // Placeholder objects represent classes currently being loaded.
109 // All threads examining the placeholder table must hold the
110 // SystemDictionary_lock, so we don't need special precautions
111 // on store ordering here.
112 // The system dictionary is the only user of this class.
113
114 class PlaceholderEntry : public HashtableEntry<Symbol*, mtClass> {
115
116 friend class PlaceholderTable;
117
118 private:
119 ClassLoaderData* _loader_data; // initiating loader
120 Symbol* _supername;
121 JavaThread* _definer; // owner of define token
122 InstanceKlass* _instanceKlass; // InstanceKlass from successful define
123 SeenThread* _superThreadQ; // doubly-linked queue of Threads loading a superclass for this class
124 SeenThread* _loadInstanceThreadQ; // loadInstance thread
125 // This can't be multiple threads since class loading waits for
126 // this token to be removed.
127
128 SeenThread* _defineThreadQ; // queue of Threads trying to define this class
129 // including _definer
130 // _definer owns token
131 // queue waits for and returns results from _definer
132 SeenThread* _inlineTypeFieldQ; // queue of inline types for circularity checking
133
134 SeenThread* actionToQueue(PlaceholderTable::classloadAction action);
135 void set_threadQ(SeenThread* seenthread, PlaceholderTable::classloadAction action);
136 void add_seen_thread(JavaThread* thread, PlaceholderTable::classloadAction action);
137 bool remove_seen_thread(JavaThread* thread, PlaceholderTable::classloadAction action);
138
139 public:
140 // Simple accessors, used only by SystemDictionary
141 Symbol* klassname() const { return literal(); }
142
143 ClassLoaderData* loader_data() const { return _loader_data; }
144 void set_loader_data(ClassLoaderData* loader_data) { _loader_data = loader_data; }
145
146 Symbol* supername() const { return _supername; }
147 void set_supername(Symbol* supername) {
148 _supername = supername;
149 if (_supername != NULL) _supername->increment_refcount();
150 }
151
152 JavaThread* definer() const {return _definer; }
153 void set_definer(JavaThread* definer) { _definer = definer; }
154
155 InstanceKlass* instance_klass() const {return _instanceKlass; }
156 void set_instance_klass(InstanceKlass* ik) { _instanceKlass = ik; }
157
158 SeenThread* superThreadQ() const { return _superThreadQ; }
159 void set_superThreadQ(SeenThread* SeenThread) { _superThreadQ = SeenThread; }
160
161 SeenThread* loadInstanceThreadQ() const { return _loadInstanceThreadQ; }
162 void set_loadInstanceThreadQ(SeenThread* SeenThread) { _loadInstanceThreadQ = SeenThread; }
163
164 SeenThread* defineThreadQ() const { return _defineThreadQ; }
165 void set_defineThreadQ(SeenThread* SeenThread) { _defineThreadQ = SeenThread; }
166
167 SeenThread* inlineTypeFieldQ() const { return _inlineTypeFieldQ; }
168 void set_inlineTypeFieldQ(SeenThread* SeenThread) { _inlineTypeFieldQ = SeenThread; }
169
170 PlaceholderEntry* next() const {
171 return (PlaceholderEntry*)HashtableEntry<Symbol*, mtClass>::next();
172 }
173
174 PlaceholderEntry** next_addr() {
175 return (PlaceholderEntry**)HashtableEntry<Symbol*, mtClass>::next_addr();
176 }
177
178 // Test for equality
179 // Entries are unique for class/classloader name pair
180 bool equals(Symbol* class_name, ClassLoaderData* loader) const {
181 return (klassname() == class_name && loader_data() == loader);
182 }
183
184 bool super_load_in_progress() {
185 return (_superThreadQ != NULL);
186 }
187
188 bool instance_load_in_progress() {
189 return (_loadInstanceThreadQ != NULL);
190 }
191
192 bool define_class_in_progress() {
193 return (_defineThreadQ != NULL);
194 }
195
196 bool inline_type_field_in_progress() {
197 return (_inlineTypeFieldQ != NULL);
198 }
199
200 // Used for ClassCircularityError checking
201 bool check_seen_thread(JavaThread* thread, PlaceholderTable::classloadAction action);
202
203 // Print method doesn't append a cr
204 void print_entry(outputStream* st) const;
205 void verify() const;
206 };
207
208 #endif // SHARE_CLASSFILE_PLACEHOLDERS_HPP