1 /*
2 * Copyright (c) 1998, 2024, 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,
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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
34 class LogStream;
35 class ObjectMonitor;
36 class ThreadsList;
37
38 class MonitorList {
39 friend class VMStructs;
40
41 private:
42 ObjectMonitor* volatile _head;
43 volatile size_t _count;
44 volatile size_t _max;
45
46 public:
47 void add(ObjectMonitor* monitor);
48 size_t unlink_deflated(Thread* current, LogStream* ls, elapsedTimer* timer_p,
49 GrowableArray<ObjectMonitor*>* unlinked_list);
50 size_t count() const;
51 size_t max() const;
52
53 class Iterator;
54 Iterator iterator() const;
55 };
56
57 class MonitorList::Iterator {
58 ObjectMonitor* _current;
59
60 public:
61 Iterator(ObjectMonitor* head) : _current(head) {}
62 bool has_next() const { return _current != NULL; }
63 ObjectMonitor* next();
64 };
65
66 class ObjectSynchronizer : AllStatic {
67 friend class VMStructs;
68
69 public:
70 typedef enum {
71 inflate_cause_vm_internal = 0,
72 inflate_cause_monitor_enter = 1,
73 inflate_cause_wait = 2,
74 inflate_cause_notify = 3,
75 inflate_cause_hash_code = 4,
76 inflate_cause_jni_enter = 5,
77 inflate_cause_jni_exit = 6,
78 inflate_cause_nof = 7 // Number of causes
79 } InflateCause;
80
81 typedef enum {
82 NOT_ENABLED = 0,
83 FATAL_EXIT = 1,
84 LOG_WARNING = 2
85 } SyncDiagnosticOption;
86
87 // exit must be implemented non-blocking, since the compiler cannot easily handle
88 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
89
90 // This is the "slow path" version of monitor enter and exit.
91 static void enter(Handle obj, BasicLock* lock, JavaThread* current);
92 static void exit(oop obj, BasicLock* lock, JavaThread* current);
93 // Used to enter a monitor for another thread. This requires that the
94 // locking_thread is suspended, and that entering on a potential
95 // inflated monitor may only contend with deflation. That is the obj being
96 // locked on is either already locked by the locking_thread or cannot
97 // escape the locking_thread.
98 static void enter_for(Handle obj, BasicLock* lock, JavaThread* locking_thread);
99 private:
100 // Shared implementation for enter and enter_for. Performs all but
101 // inflated monitor enter.
102 static bool enter_fast_impl(Handle obj, BasicLock* lock, JavaThread* locking_thread);
103
104 public:
105 // Used only to handle jni locks or other unmatched monitor enter/exit
106 // Internally they will use heavy weight monitor.
107 static void jni_enter(Handle obj, JavaThread* current);
108 static void jni_exit(oop obj, TRAPS);
109
110 // Handle all interpreter, compiler and jni cases
111 static int wait(Handle obj, jlong millis, TRAPS);
112 static void notify(Handle obj, TRAPS);
113 static void notifyall(Handle obj, TRAPS);
114
115 static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
116 static bool quick_enter(oop obj, JavaThread* current, BasicLock* Lock);
117
118 // Special internal-use-only method for use by JVM infrastructure
119 // that needs to wait() on a java-level object but must not respond
120 // to interrupt requests and doesn't timeout.
121 static void wait_uninterruptibly(Handle obj, JavaThread* current);
122
123 // used by classloading to free classloader object lock,
124 // wait on an internal lock, and reclaim original lock
125 // with original recursion count
126 static intx complete_exit(Handle obj, JavaThread* current);
127 static void reenter (Handle obj, intx recursions, JavaThread* current);
128
129 // Inflate light weight monitor to heavy weight monitor
130 static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
131 // Used to inflate a monitor as if it was done from the thread JavaThread.
132 static ObjectMonitor* inflate_for(JavaThread* thread, oop obj, const InflateCause cause);
133
134 private:
135 // Shared implementation between the different LockingMode.
136 static ObjectMonitor* inflate_impl(JavaThread* thread, oop obj, const InflateCause cause);
137
138 public:
139 // This version is only for internal use
140 static void inflate_helper(oop obj);
141 static const char* inflate_cause_name(const InflateCause cause);
142
143 // Returns the identity hash value for an oop
144 // NOTE: It may cause monitor inflation
145 static intptr_t identity_hash_value_for(Handle obj);
146 static intptr_t FastHashCode(Thread* current, oop obj);
147
148 // java.lang.Thread support
149 static bool current_thread_holds_lock(JavaThread* current, Handle h_obj);
150
151 static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
152
153 // JNI detach support
154 static void release_monitors_owned_by_thread(JavaThread* current);
155 static void monitors_iterate(MonitorClosure* m, JavaThread* thread);
156
157 // Initialize the gInflationLocks
158 static void initialize();
159
160 // GC: we current use aggressive monitor deflation policy
161 // Basically we try to deflate all monitors that are not busy.
162 static size_t deflate_idle_monitors();
163
164 // Deflate idle monitors:
165 static void chk_for_block_req(JavaThread* current, const char* op_name,
166 const char* cnt_name, size_t cnt, LogStream* ls,
167 elapsedTimer* timer_p);
168 static size_t deflate_monitor_list(Thread* current, LogStream* ls,
169 elapsedTimer* timer_p);
170 static size_t in_use_list_ceiling();
171 static void dec_in_use_list_ceiling();
172 static void inc_in_use_list_ceiling();
173 static void set_in_use_list_ceiling(size_t new_value);
174 static bool is_async_deflation_needed();
175 static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
176 static bool is_final_audit() { return _is_final_audit; }
177 static void set_is_final_audit() { _is_final_audit = true; }
178 static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
179 static bool request_deflate_idle_monitors(); // for whitebox test support
180 static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
181 static jlong time_since_last_async_deflation_ms();
182
183 // debugging
184 static void audit_and_print_stats(bool on_exit);
185 static void chk_in_use_list(outputStream* out, int* error_cnt_p);
186 static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
187 int* error_cnt_p);
188 static void do_final_audit_and_print_stats();
189 static void log_in_use_monitor_details(outputStream* out);
190
191 private:
192 friend class SynchronizerTest;
193
194 static MonitorList _in_use_list;
195 static volatile bool _is_async_deflation_requested;
196 static volatile bool _is_final_audit;
197 static jlong _last_async_deflation_time_ns;
198
199 // Support for SynchronizerTest access to GVars fields:
200 static u_char* get_gvars_addr();
201 static u_char* get_gvars_hc_sequence_addr();
202 static size_t get_gvars_size();
203 static u_char* get_gvars_stw_random_addr();
204
205 static void handle_sync_on_value_based_class(Handle obj, JavaThread* locking_thread);
206 };
207
208 // ObjectLocker enforces balanced locking and can never throw an
209 // IllegalMonitorStateException. However, a pending exception may
210 // have to pass through, and we must also be able to deal with
211 // asynchronous exceptions. The caller is responsible for checking
212 // the thread's pending exception if needed.
213 class ObjectLocker : public StackObj {
214 private:
215 JavaThread* _thread;
216 Handle _obj;
217 BasicLock _lock;
218 public:
219 ObjectLocker(Handle obj, JavaThread* current);
220 ~ObjectLocker();
221
222 // Monitor behavior
223 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
224 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
225 void wait_uninterruptibly(JavaThread* current) { ObjectSynchronizer::wait_uninterruptibly(_obj, current); }
226 };
227
228 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP