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,
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_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 "runtime/javaThread.hpp"
33 #include "utilities/resourceHash.hpp"
34
35 template <typename T> class GrowableArray;
36 class LogStream;
37 class ObjectMonitor;
38 class ObjectMonitorDeflationSafepointer;
39 class ThreadsList;
40
41 class MonitorList {
42 friend class VMStructs;
43
44 private:
45 ObjectMonitor* volatile _head;
46 volatile size_t _count;
47 volatile size_t _max;
48
49 public:
50 void add(ObjectMonitor* monitor);
51 size_t unlink_deflated(size_t deflated_count,
52 GrowableArray<ObjectMonitor*>* unlinked_list,
53 ObjectMonitorDeflationSafepointer* safepointer);
54 size_t count() const;
55 size_t max() const;
56
57 class Iterator;
58 Iterator iterator() const;
59 };
60
61 class MonitorList::Iterator {
62 ObjectMonitor* _current;
63
64 public:
65 Iterator(ObjectMonitor* head) : _current(head) {}
66 bool has_next() const { return _current != nullptr; }
67 ObjectMonitor* next();
68 };
69
70 class ObjectSynchronizer : AllStatic {
71 friend class VMStructs;
72 friend class ObjectMonitorDeflationLogging;
73
74 public:
75 typedef enum {
76 inflate_cause_vm_internal = 0,
77 inflate_cause_monitor_enter = 1,
78 inflate_cause_wait = 2,
79 inflate_cause_notify = 3,
80 inflate_cause_hash_code = 4,
81 inflate_cause_jni_enter = 5,
82 inflate_cause_jni_exit = 6,
83 inflate_cause_nof = 7 // Number of causes
84 } InflateCause;
85
86 typedef enum {
87 NOT_ENABLED = 0,
88 FATAL_EXIT = 1,
89 LOG_WARNING = 2
90 } SyncDiagnosticOption;
91
92 // exit must be implemented non-blocking, since the compiler cannot easily handle
93 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
94
95 // This is the "slow path" version of monitor enter and exit.
96 static inline void enter(Handle obj, BasicLock* lock, JavaThread* current);
97 static inline void exit(oop obj, BasicLock* lock, JavaThread* current);
98
99 // Used to enter a monitor for another thread. This requires that the
100 // locking_thread is suspended, and that entering on a potential
101 // inflated monitor may only contend with deflation. That is the obj being
102 // locked on is either already locked by the locking_thread or cannot
103 // escape the locking_thread.
104 static void enter_for(Handle obj, BasicLock* lock, JavaThread* locking_thread);
105 private:
106 // Shared implementation for enter and enter_for. Performs all but
107 // inflated monitor enter.
108 static bool enter_fast_impl(Handle obj, BasicLock* lock, JavaThread* locking_thread);
109
110 static bool quick_enter_legacy(oop obj, JavaThread* current, BasicLock* Lock);
111 static void enter_legacy(Handle obj, BasicLock* Lock, JavaThread* current);
112 static void exit_legacy(oop obj, BasicLock* lock, JavaThread* current);
113 public:
114 // Used only to handle jni locks or other unmatched monitor enter/exit
115 // Internally they will use heavy weight monitor.
116 static void jni_enter(Handle obj, JavaThread* current);
117 static void jni_exit(oop obj, TRAPS);
118
119 // Handle all interpreter, compiler and jni cases
120 static int wait(Handle obj, jlong millis, TRAPS);
121 static void notify(Handle obj, TRAPS);
122 static void notifyall(Handle obj, TRAPS);
123
124 static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
125 static inline bool quick_enter(oop obj, JavaThread* current, BasicLock* Lock);
126
127 // Inflate light weight monitor to heavy weight monitor
128 static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
129 // Used to inflate a monitor as if it was done from the thread JavaThread.
130 static ObjectMonitor* inflate_for(JavaThread* thread, oop obj, const InflateCause cause);
131
132 private:
133 // Shared implementation between the different LockingMode.
134 static ObjectMonitor* inflate_impl(oop obj, const InflateCause cause);
135
136 public:
137 // This version is only for internal use
138 static void inflate_helper(oop obj);
139 static const char* inflate_cause_name(const InflateCause cause);
140
141 inline static ObjectMonitor* read_monitor(markWord mark);
142 inline static ObjectMonitor* read_monitor(Thread* current, oop obj, markWord mark);
143
144 // Returns the identity hash value for an oop
145 // NOTE: It may cause monitor inflation
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
156 // Iterate over all ObjectMonitors.
157 template <typename Function>
158 static void monitors_iterate(Function function);
159
160 // Iterate ObjectMonitors owned by any thread and where the owner `filter`
161 // returns true.
162 template <typename OwnerFilter>
163 static void owned_monitors_iterate_filtered(MonitorClosure* closure, OwnerFilter filter);
164
165 // Iterate ObjectMonitors where the owner == thread; this does NOT include
166 // ObjectMonitors where owner is set to a stack lock address in thread.
167 static void owned_monitors_iterate(MonitorClosure* m, JavaThread* thread);
168
169 // Iterate ObjectMonitors owned by any thread.
170 static void owned_monitors_iterate(MonitorClosure* closure);
171
172 // Initialize the gInflationLocks
173 static void initialize();
174
175 // We currently use aggressive monitor deflation policy;
176 // basically we try to deflate all monitors that are not busy.
177 static size_t deflate_idle_monitors();
178
179 // Deflate idle monitors:
180 static size_t deflate_monitor_list(ObjectMonitorDeflationSafepointer* safepointer);
181 static size_t in_use_list_ceiling();
182 static void dec_in_use_list_ceiling();
183 static void inc_in_use_list_ceiling();
184 static void set_in_use_list_ceiling(size_t new_value);
185 static bool is_async_deflation_needed();
186 static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
187 static bool is_final_audit() { return _is_final_audit; }
188 static void set_is_final_audit() { _is_final_audit = true; }
189 static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
190 static void request_deflate_idle_monitors();
191 static bool request_deflate_idle_monitors_from_wb(); // for whitebox test support
192 static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
193 static jlong time_since_last_async_deflation_ms();
194
195 // debugging
196 static void audit_and_print_stats(outputStream* out, bool on_exit);
197 static void chk_in_use_list(outputStream* out, int* error_cnt_p);
198 static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
199 int* error_cnt_p);
200 static void do_final_audit_and_print_stats();
201 static void log_in_use_monitor_details(outputStream* out, bool log_all);
202
203 private:
204 friend class SynchronizerTest;
205 friend class LightweightSynchronizer;
206
207 static MonitorList _in_use_list;
208 static volatile bool _is_async_deflation_requested;
209 static volatile bool _is_final_audit;
210 static jlong _last_async_deflation_time_ns;
211
212 // Support for SynchronizerTest access to GVars fields:
213 static u_char* get_gvars_addr();
214 static u_char* get_gvars_hc_sequence_addr();
215 static size_t get_gvars_size();
216 static u_char* get_gvars_stw_random_addr();
217
218 static void handle_sync_on_value_based_class(Handle obj, JavaThread* locking_thread);
219 };
220
221 // ObjectLocker enforces balanced locking and can never throw an
222 // IllegalMonitorStateException. However, a pending exception may
223 // have to pass through, and we must also be able to deal with
224 // asynchronous exceptions. The caller is responsible for checking
225 // the thread's pending exception if needed.
226 class ObjectLocker : public StackObj {
227 private:
228 JavaThread* _thread;
229 Handle _obj;
230 BasicLock _lock;
231 public:
232 ObjectLocker(Handle obj, JavaThread* current);
233 ~ObjectLocker();
234
235 // Monitor behavior
236 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
237 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
238 };
239
240 // Interface to visit monitors
241 class ObjectMonitorsView {
242 public:
243 // Visit monitors that belong to the given thread
244 virtual void visit(MonitorClosure* closure, JavaThread* thread) = 0;
245 };
246
247 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP