1 /*
2 * Copyright (c) 1998, 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.
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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_RUNTIME_SYNCHRONIZER_HPP
26 #define SHARE_RUNTIME_SYNCHRONIZER_HPP
27
28 #include "memory/padded.hpp"
29 #include "oops/markWord.hpp"
30 #include "runtime/basicLock.hpp"
31 #include "runtime/handles.hpp"
32 #include "utilities/growableArray.hpp"
33 #include "utilities/linkedlist.hpp"
34 #include "utilities/resourceHash.hpp"
35
36 class LogStream;
37 class ObjectMonitor;
38 class ThreadsList;
39
40 // Hash table of void* to a list of ObjectMonitor* owned by the JavaThread.
41 // The JavaThread's owner key is either a JavaThread* or a stack lock
42 // address in the JavaThread so we use "void*".
43 //
44 class ObjectMonitorsHashtable {
45 private:
46 static unsigned int ptr_hash(void* const& s1) {
47 // 2654435761 = 2^32 * Phi (golden ratio)
48 return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u);
49 }
50
51 public:
52 typedef LinkedListImpl<ObjectMonitor*,
53 ResourceObj::C_HEAP, mtThread,
54 AllocFailStrategy::RETURN_NULL> PtrList;
55
56 // ResourceHashtable SIZE is specified at compile time so we
57 // use 1031 which is the first prime after 1024.
58 typedef ResourceHashtable<void*, PtrList*, 1031, ResourceObj::C_HEAP, mtThread,
59 &ObjectMonitorsHashtable::ptr_hash> PtrTable;
60 private:
61 PtrTable* _ptrs;
62 size_t _key_count;
63 size_t _om_count;
64
65 public:
66 // ResourceHashtable is passed to various functions and populated in
67 // different places so we allocate it using C_HEAP to make it immune
68 // from any ResourceMarks that happen to be in the code paths.
69 ObjectMonitorsHashtable() : _ptrs(new (ResourceObj::C_HEAP, mtThread) PtrTable()), _key_count(0), _om_count(0) {}
70
71 ~ObjectMonitorsHashtable();
72
73 void add_entry(void* key, ObjectMonitor* om);
74
75 void add_entry(void* key, PtrList* list) {
76 _ptrs->put(key, list);
77 _key_count++;
78 }
79
80 PtrList* get_entry(void* key) {
81 PtrList** listpp = _ptrs->get(key);
82 return (listpp == nullptr) ? nullptr : *listpp;
83 }
84
85 bool has_entry(void* key) {
86 PtrList** listpp = _ptrs->get(key);
87 return listpp != nullptr && *listpp != nullptr;
88 }
89
90 bool has_entry(void* key, ObjectMonitor* om);
91
92 size_t key_count() { return _key_count; }
93 size_t om_count() { return _om_count; }
94 };
95
96 class MonitorList {
97 friend class VMStructs;
98
99 private:
100 ObjectMonitor* volatile _head;
101 volatile size_t _count;
102 volatile size_t _max;
103
104 public:
105 void add(ObjectMonitor* monitor);
106 size_t unlink_deflated(Thread* current, LogStream* ls, elapsedTimer* timer_p,
107 GrowableArray<ObjectMonitor*>* unlinked_list);
108 size_t count() const;
109 size_t max() const;
110
111 class Iterator;
112 Iterator iterator() const;
113 };
114
115 class MonitorList::Iterator {
116 ObjectMonitor* _current;
117
118 public:
119 Iterator(ObjectMonitor* head) : _current(head) {}
120 bool has_next() const { return _current != NULL; }
121 ObjectMonitor* next();
122 };
123
124 class ObjectSynchronizer : AllStatic {
125 friend class VMStructs;
126
127 public:
128 typedef enum {
129 inflate_cause_vm_internal = 0,
130 inflate_cause_monitor_enter = 1,
131 inflate_cause_wait = 2,
132 inflate_cause_notify = 3,
133 inflate_cause_hash_code = 4,
134 inflate_cause_jni_enter = 5,
135 inflate_cause_jni_exit = 6,
136 inflate_cause_nof = 7 // Number of causes
137 } InflateCause;
138
139 typedef enum {
140 NOT_ENABLED = 0,
141 FATAL_EXIT = 1,
142 LOG_WARNING = 2
143 } SyncDiagnosticOption;
144
145 // exit must be implemented non-blocking, since the compiler cannot easily handle
146 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
147
148 // This is the "slow path" version of monitor enter and exit.
149 static void enter(Handle obj, BasicLock* lock, JavaThread* current);
150 static void exit(oop obj, BasicLock* lock, JavaThread* current);
151
152 // Used only to handle jni locks or other unmatched monitor enter/exit
153 // Internally they will use heavy weight monitor.
154 static void jni_enter(Handle obj, JavaThread* current);
155 static void jni_exit(oop obj, TRAPS);
156
157 // Handle all interpreter, compiler and jni cases
158 static int wait(Handle obj, jlong millis, TRAPS);
159 static void notify(Handle obj, TRAPS);
160 static void notifyall(Handle obj, TRAPS);
161
162 static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
163 static bool quick_enter(oop obj, JavaThread* current, BasicLock* Lock);
164
165 // Special internal-use-only method for use by JVM infrastructure
166 // that needs to wait() on a java-level object but must not respond
167 // to interrupt requests and doesn't timeout.
168 static void wait_uninterruptibly(Handle obj, JavaThread* current);
169
170 // used by classloading to free classloader object lock,
171 // wait on an internal lock, and reclaim original lock
172 // with original recursion count
173 static intx complete_exit(Handle obj, JavaThread* current);
174 static void reenter (Handle obj, intx recursions, JavaThread* current);
175
176 // Inflate light weight monitor to heavy weight monitor
177 static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
178 // This version is only for internal use
179 static void inflate_helper(oop obj);
180 static const char* inflate_cause_name(const InflateCause cause);
181
182 // Returns the identity hash value for an oop
183 // NOTE: It may cause monitor inflation
184 static intptr_t identity_hash_value_for(Handle obj);
185 static intptr_t FastHashCode(Thread* current, oop obj);
186
187 // Read mark-word and spin-wait as long as INFLATING is observed.
188 static markWord read_stable_mark(oop obj);
189
190 static markWord stable_mark(oop obj);
191
192 // java.lang.Thread support
193 static bool current_thread_holds_lock(JavaThread* current, Handle h_obj);
194
195 static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
196
197 // JNI detach support
198 static void release_monitors_owned_by_thread(JavaThread* current);
199
200 // Iterate ObjectMonitors where the owner == thread; this does NOT include
201 // ObjectMonitors where owner is set to a stack lock address in thread:
202 //
203 // This version of monitors_iterate() works with the in-use monitor list.
204 static void monitors_iterate(MonitorClosure* m, JavaThread* thread);
205 // This version of monitors_iterate() works with the specified linked list.
206 static void monitors_iterate(MonitorClosure* closure,
207 ObjectMonitorsHashtable::PtrList* list,
208 JavaThread* thread);
209
210 // Initialize the gInflationLocks
211 static void initialize();
212
213 // GC: we currently use aggressive monitor deflation policy
214 // Basically we try to deflate all monitors that are not busy.
215 static size_t deflate_idle_monitors(ObjectMonitorsHashtable* table);
216
217 // Deflate idle monitors:
218 static void chk_for_block_req(JavaThread* current, const char* op_name,
219 const char* cnt_name, size_t cnt, LogStream* ls,
220 elapsedTimer* timer_p);
221 static size_t deflate_monitor_list(Thread* current, LogStream* ls, elapsedTimer* timer_p,
222 ObjectMonitorsHashtable* table);
223 static size_t in_use_list_ceiling();
224 static void dec_in_use_list_ceiling();
225 static void inc_in_use_list_ceiling();
226 static void set_in_use_list_ceiling(size_t new_value);
227 static bool is_async_deflation_needed();
228 static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
229 static bool is_final_audit() { return _is_final_audit; }
230 static void set_is_final_audit() { _is_final_audit = true; }
231 static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
232 static bool request_deflate_idle_monitors(); // for whitebox test support
233 static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
234 static jlong time_since_last_async_deflation_ms();
235
236 // debugging
237 static void audit_and_print_stats(bool on_exit);
238 static void chk_in_use_list(outputStream* out, int* error_cnt_p);
239 static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
240 int* error_cnt_p);
241 static void do_final_audit_and_print_stats();
242 static void log_in_use_monitor_details(outputStream* out);
243
244 private:
245 friend class SynchronizerTest;
246
247 static MonitorList _in_use_list;
248 static volatile bool _is_async_deflation_requested;
249 static volatile bool _is_final_audit;
250 static jlong _last_async_deflation_time_ns;
251
252 // Support for SynchronizerTest access to GVars fields:
253 static u_char* get_gvars_addr();
254 static u_char* get_gvars_hc_sequence_addr();
255 static size_t get_gvars_size();
256 static u_char* get_gvars_stw_random_addr();
257
258 static void handle_sync_on_value_based_class(Handle obj, JavaThread* current);
259 };
260
261 // ObjectLocker enforces balanced locking and can never throw an
262 // IllegalMonitorStateException. However, a pending exception may
263 // have to pass through, and we must also be able to deal with
264 // asynchronous exceptions. The caller is responsible for checking
265 // the thread's pending exception if needed.
266 class ObjectLocker : public StackObj {
267 private:
268 JavaThread* _thread;
269 Handle _obj;
270 BasicLock _lock;
271 public:
272 ObjectLocker(Handle obj, JavaThread* current);
273 ~ObjectLocker();
274
275 // Monitor behavior
276 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
277 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
278 void wait_uninterruptibly(JavaThread* current) { ObjectSynchronizer::wait_uninterruptibly(_obj, current); }
279 };
280
281 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP