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.
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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/resourceHash.hpp"
33
34 template <typename T> class GrowableArray;
35 class LogStream;
36 class ObjectMonitor;
37 class ObjectMonitorDeflationSafepointer;
38 class ThreadsList;
39
40 class MonitorList {
41 friend class VMStructs;
42
43 private:
44 ObjectMonitor* volatile _head;
45 volatile size_t _count;
46 volatile size_t _max;
47
48 public:
49 void add(ObjectMonitor* monitor);
50 size_t unlink_deflated(size_t deflated_count,
51 GrowableArray<ObjectMonitor*>* unlinked_list,
52 ObjectMonitorDeflationSafepointer* safepointer);
53 size_t count() const;
54 size_t max() const;
55
56 class Iterator;
57 Iterator iterator() const;
58 };
59
60 class MonitorList::Iterator {
61 ObjectMonitor* _current;
62
63 public:
64 Iterator(ObjectMonitor* head) : _current(head) {}
65 bool has_next() const { return _current != nullptr; }
66 ObjectMonitor* next();
67 };
68
69 class ObjectSynchronizer : AllStatic {
70 friend class VMStructs;
71 friend class ObjectMonitorDeflationLogging;
72
73 public:
74 typedef enum {
75 inflate_cause_vm_internal = 0,
76 inflate_cause_monitor_enter = 1,
77 inflate_cause_wait = 2,
78 inflate_cause_notify = 3,
79 inflate_cause_hash_code = 4,
80 inflate_cause_jni_enter = 5,
81 inflate_cause_jni_exit = 6,
82 inflate_cause_cont_freeze = 7,
83 inflate_cause_nof = 8 // 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 void enter(Handle obj, BasicLock* lock, JavaThread* current);
97 static void exit(oop obj, BasicLock* lock, JavaThread* current);
98 // Used to enter a monitor for another thread. This requires that the
99 // locking_thread is suspended, and that entering on a potential
100 // inflated monitor may only contend with deflation. That is the obj being
101 // locked on is either already locked by the locking_thread or cannot
102 // escape the locking_thread.
103 static void enter_for(Handle obj, BasicLock* lock, JavaThread* locking_thread);
104 private:
105 // Shared implementation for enter and enter_for. Performs all but
106 // inflated monitor enter.
107 static bool enter_fast_impl(Handle obj, BasicLock* lock, JavaThread* locking_thread);
108
109 public:
110 // Used only to handle jni locks or other unmatched monitor enter/exit
111 // Internally they will use heavy weight monitor.
112 static void jni_enter(Handle obj, JavaThread* current);
113 static void jni_exit(oop obj, TRAPS);
114
115 // Handle all interpreter, compiler and jni cases
116 static int wait(Handle obj, jlong millis, TRAPS);
117 static void notify(Handle obj, TRAPS);
118 static void notifyall(Handle obj, TRAPS);
119
120 static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
121 static bool quick_enter(oop obj, JavaThread* current, BasicLock* Lock);
122
123 // Inflate light weight monitor to heavy weight monitor
124 static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
125 // Used to inflate a monitor as if it was done from the thread JavaThread.
126 static ObjectMonitor* inflate_for(JavaThread* thread, oop obj, const InflateCause cause);
127
128 private:
129 // Shared implementation between the different LockingMode.
130 static ObjectMonitor* inflate_impl(JavaThread* thread, oop obj, const InflateCause cause);
131
132 public:
133 // This version is only for internal use
134 static void inflate_helper(oop obj);
135 static const char* inflate_cause_name(const InflateCause cause);
136
137 // Returns the identity hash value for an oop
138 // NOTE: It may cause monitor inflation
139 static intptr_t FastHashCode(Thread* current, oop obj);
140
141 // java.lang.Thread support
142 static bool current_thread_holds_lock(JavaThread* current, Handle h_obj);
143
144 static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
145
146 // JNI detach support
147 static void release_monitors_owned_by_thread(JavaThread* current);
148
149 // Iterate over all ObjectMonitors.
150 template <typename Function>
151 static void monitors_iterate(Function function);
152
153 // Iterate ObjectMonitors owned by any thread and where the owner `filter`
154 // returns true.
155 template <typename OwnerFilter>
156 static void owned_monitors_iterate_filtered(MonitorClosure* closure, OwnerFilter filter);
157
158 // Iterate ObjectMonitors where the owner == thread; this does NOT include
159 // ObjectMonitors where owner is set to a stack lock address in thread.
160 static void owned_monitors_iterate(MonitorClosure* m, JavaThread* thread);
161
162 // Iterate ObjectMonitors owned by any thread.
163 static void owned_monitors_iterate(MonitorClosure* closure);
164
165 // Initialize the gInflationLocks
166 static void initialize();
167
168 // We currently use aggressive monitor deflation policy;
169 // basically we try to deflate all monitors that are not busy.
170 static size_t deflate_idle_monitors();
171
172 // Deflate idle monitors:
173 static size_t deflate_monitor_list(ObjectMonitorDeflationSafepointer* safepointer);
174 static size_t in_use_list_ceiling();
175 static void dec_in_use_list_ceiling();
176 static void inc_in_use_list_ceiling();
177 static void set_in_use_list_ceiling(size_t new_value);
178 static bool is_async_deflation_needed();
179 static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
180 static bool is_final_audit() { return _is_final_audit; }
181 static void set_is_final_audit() { _is_final_audit = true; }
182 static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
183 static void request_deflate_idle_monitors();
184 static bool request_deflate_idle_monitors_from_wb(); // for whitebox test support
185 static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
186 static jlong time_since_last_async_deflation_ms();
187
188 // debugging
189 static void audit_and_print_stats(outputStream* out, bool on_exit);
190 static void chk_in_use_list(outputStream* out, int* error_cnt_p);
191 static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
192 int* error_cnt_p);
193 static void do_final_audit_and_print_stats();
194 static void log_in_use_monitor_details(outputStream* out, bool log_all);
195
196 private:
197 friend class SynchronizerTest;
198
199 static MonitorList _in_use_list;
200 static volatile bool _is_async_deflation_requested;
201 static volatile bool _is_final_audit;
202 static jlong _last_async_deflation_time_ns;
203
204 // Support for SynchronizerTest access to GVars fields:
205 static u_char* get_gvars_addr();
206 static u_char* get_gvars_hc_sequence_addr();
207 static size_t get_gvars_size();
208 static u_char* get_gvars_stw_random_addr();
209
210 static void handle_sync_on_value_based_class(Handle obj, JavaThread* locking_thread);
211 };
212
213 // ObjectLocker enforces balanced locking and can never throw an
214 // IllegalMonitorStateException. However, a pending exception may
215 // have to pass through, and we must also be able to deal with
216 // asynchronous exceptions. The caller is responsible for checking
217 // the thread's pending exception if needed.
218 class ObjectLocker : public StackObj {
219 private:
220 JavaThread* _thread;
221 Handle _obj;
222 BasicLock _lock;
223 public:
224 ObjectLocker(Handle obj, JavaThread* current);
225 ~ObjectLocker();
226
227 // Monitor behavior
228 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
229 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
230 };
231
232 // Interface to visit monitors
233 class ObjectMonitorsView {
234 public:
235 // Visit monitors that belong to the given thread
236 virtual void visit(MonitorClosure* closure, JavaThread* thread) = 0;
237 };
238
239 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP