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 "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 MonitorList() : _head(nullptr), _count(0), _max(0) {};
51 void add(ObjectMonitor* monitor);
52 size_t unlink_deflated(size_t deflated_count,
53 GrowableArray<ObjectMonitor*>* unlinked_list,
54 ObjectMonitorDeflationSafepointer* safepointer);
55 size_t count() const;
56 size_t max() const;
57
58 class Iterator;
59 Iterator iterator() const;
60 };
61
62 class MonitorList::Iterator {
63 ObjectMonitor* _current;
64
65 public:
66 Iterator(ObjectMonitor* head) : _current(head) {}
67 bool has_next() const { return _current != nullptr; }
68 ObjectMonitor* next();
69 };
70
71 class ObjectSynchronizer : AllStatic {
72 friend class VMStructs;
73 friend class ObjectMonitorDeflationLogging;
74 friend class WhiteBox;
75
76 public:
77 typedef enum {
78 inflate_cause_vm_internal = 0,
79 inflate_cause_monitor_enter = 1,
80 inflate_cause_wait = 2,
81 inflate_cause_notify = 3,
82 inflate_cause_hash_code = 4,
83 inflate_cause_jni_enter = 5,
84 inflate_cause_jni_exit = 6,
85 inflate_cause_nof = 7 // Number of causes
86 } InflateCause;
87
88 typedef enum {
89 NOT_ENABLED = 0,
90 FATAL_EXIT = 1,
91 LOG_WARNING = 2
92 } SyncDiagnosticOption;
93
94 // exit must be implemented non-blocking, since the compiler cannot easily handle
95 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
96
97 // This is the "slow path" version of monitor enter and exit.
98 static inline void enter(Handle obj, BasicLock* lock, JavaThread* current);
99 static inline void exit(oop obj, BasicLock* lock, JavaThread* current);
100
101 // Used to enter a monitor for another thread. This requires that the
102 // locking_thread is suspended, and that entering on a potential
103 // inflated monitor may only contend with deflation. That is the obj being
104 // locked on is either already locked by the locking_thread or cannot
105 // escape the locking_thread.
106 static void enter_for(Handle obj, BasicLock* lock, JavaThread* locking_thread);
107 private:
108 // Shared implementation for enter and enter_for. Performs all but
109 // inflated monitor enter.
110 static bool enter_fast_impl(Handle obj, BasicLock* lock, JavaThread* locking_thread);
111
112 static bool quick_enter_legacy(oop obj, BasicLock* Lock, JavaThread* current);
113 static void enter_legacy(Handle obj, BasicLock* Lock, JavaThread* current);
114 static void exit_legacy(oop obj, BasicLock* lock, JavaThread* current);
115 public:
116 // Used only to handle jni locks or other unmatched monitor enter/exit
117 // Internally they will use heavy weight monitor.
118 static void jni_enter(Handle obj, JavaThread* current);
119 static void jni_exit(oop obj, TRAPS);
120
121 // Handle all interpreter, compiler and jni cases
122 static int wait(Handle obj, jlong millis, TRAPS);
123 static void notify(Handle obj, TRAPS);
124 static void notifyall(Handle obj, TRAPS);
125
126 static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
127 static inline bool quick_enter(oop obj, BasicLock* Lock, JavaThread* current);
128
129 // Special internal-use-only method for use by JVM infrastructure
130 // that needs to wait() on a java-level object but that can't risk
131 // throwing unexpected InterruptedExecutionExceptions.
132 static void waitUninterruptibly(Handle obj, jlong Millis, TRAPS);
133
134 // Inflate light weight monitor to heavy weight monitor
135 static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
136 // Used to inflate a monitor as if it was done from the thread JavaThread.
137 static ObjectMonitor* inflate_for(JavaThread* thread, oop obj, const InflateCause cause);
138
139 private:
140 // Shared implementation between the different LockingMode.
141 static ObjectMonitor* inflate_impl(JavaThread* locking_thread, oop obj, const InflateCause cause);
142
143 public:
144 // This version is only for internal use
145 static void inflate_helper(oop obj);
146 static const char* inflate_cause_name(const InflateCause cause);
147
148 inline static ObjectMonitor* read_monitor(markWord mark);
149 inline static ObjectMonitor* read_monitor(Thread* current, oop obj, markWord mark);
150
151 // Returns the identity hash value for an oop
152 // NOTE: It may cause monitor inflation
153 static intptr_t FastHashCode(Thread* current, oop obj);
154
155 // java.lang.Thread support
156 static bool current_thread_holds_lock(JavaThread* current, Handle h_obj);
157
158 static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
159
160 // JNI detach support
161 static void release_monitors_owned_by_thread(JavaThread* current);
162
163 // Iterate over all ObjectMonitors.
164 template <typename Function>
165 static void monitors_iterate(Function function);
166
167 // Iterate ObjectMonitors owned by any thread and where the owner `filter`
168 // returns true.
169 template <typename OwnerFilter>
170 static void owned_monitors_iterate_filtered(MonitorClosure* closure, OwnerFilter filter);
171
172 // Iterate ObjectMonitors where the owner is thread; this does NOT include
173 // ObjectMonitors where the owner is anonymous.
174 static void owned_monitors_iterate(MonitorClosure* m, JavaThread* thread);
175
176 // Iterate ObjectMonitors where the owner is vthread.
177 static void owned_monitors_iterate(MonitorClosure* m, oop vthread);
178
179 // Iterate ObjectMonitors owned by any thread.
180 static void owned_monitors_iterate(MonitorClosure* closure);
181
182 // Initialize the gInflationLocks
183 static void initialize();
184
185 // We currently use aggressive monitor deflation policy;
186 // basically we try to deflate all monitors that are not busy.
187 static size_t deflate_idle_monitors();
188
189 // Deflate idle monitors:
190 static size_t deflate_monitor_list(ObjectMonitorDeflationSafepointer* safepointer);
191 static size_t in_use_list_count();
192 static size_t in_use_list_max();
193 static size_t in_use_list_ceiling();
194 static void dec_in_use_list_ceiling();
195 static void inc_in_use_list_ceiling();
196 static void set_in_use_list_ceiling(size_t new_value);
197 static bool is_async_deflation_needed();
198 static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
199 static bool is_final_audit() { return _is_final_audit; }
200 static void set_is_final_audit() { _is_final_audit = true; }
201 static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
202 static void request_deflate_idle_monitors();
203 static bool request_deflate_idle_monitors_from_wb(); // for whitebox test support
204 static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
205 static jlong time_since_last_async_deflation_ms();
206
207 // debugging
208 static void audit_and_print_stats(outputStream* out, bool on_exit);
209 static void chk_in_use_list(outputStream* out, int* error_cnt_p);
210 static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
211 int* error_cnt_p);
212 static void do_final_audit_and_print_stats();
213 static void log_in_use_monitor_details(outputStream* out, bool log_all);
214
215 static intptr_t get_next_hash(Thread* current, oop obj);
216
217 private:
218 friend class SynchronizerTest;
219 friend class LightweightSynchronizer;
220
221 static MonitorList _in_use_list;
222 static volatile bool _is_async_deflation_requested;
223 static volatile bool _is_final_audit;
224 static jlong _last_async_deflation_time_ns;
225
226 // Support for SynchronizerTest access to GVars fields:
227 static u_char* get_gvars_addr();
228 static u_char* get_gvars_hc_sequence_addr();
229 static size_t get_gvars_size();
230 static u_char* get_gvars_stw_random_addr();
231
232 static void handle_sync_on_value_based_class(Handle obj, JavaThread* locking_thread);
233 };
234
235 // ObjectLocker enforces balanced locking and can never throw an
236 // IllegalMonitorStateException. However, a pending exception may
237 // have to pass through, and we must also be able to deal with
238 // asynchronous exceptions. The caller is responsible for checking
239 // the thread's pending exception if needed.
240 // When using ObjectLocker the top native frames in the stack will
241 // not be seen in case we attempt preemption, since we start walking
242 // from the last Java anchor, so we disable it with NoPreemptMark.
243 class ObjectLocker : public StackObj {
244 private:
245 JavaThread* _thread;
246 Handle _obj;
247 BasicLock _lock;
248 NoPreemptMark _npm;
249 public:
250 ObjectLocker(Handle obj, JavaThread* current);
251 ~ObjectLocker();
252
253 // Monitor behavior
254 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
255 void wait_uninterruptibly(TRAPS) { ObjectSynchronizer::waitUninterruptibly(_obj, 0, CHECK); } // wait forever
256 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
257 };
258
259 // Interface to visit monitors
260 class ObjectMonitorsView {
261 public:
262 // Visit monitors that belong to the given thread
263 virtual void visit(MonitorClosure* closure, JavaThread* thread) = 0;
264 };
265
266 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP