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.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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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 *
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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 ThreadsList;
38
39 // Hash table of void* to a list of ObjectMonitor* owned by the JavaThread.
40 // The JavaThread's owner key is either a JavaThread* or a stack lock
41 // address in the JavaThread so we use "void*".
42 //
43 class ObjectMonitorsHashtable {
44 private:
45 static unsigned int ptr_hash(void* const& s1) {
46 // 2654435761 = 2^32 * Phi (golden ratio)
47 return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u);
48 }
49
50 public:
51 class PtrList;
52
53 private:
54 // ResourceHashtable SIZE is specified at compile time so we
55 // use 1031 which is the first prime after 1024.
56 typedef ResourceHashtable<void*, PtrList*, 1031, AnyObj::C_HEAP, mtThread,
57 &ObjectMonitorsHashtable::ptr_hash> PtrTable;
58 PtrTable* _ptrs;
59 size_t _key_count;
60 size_t _om_count;
61
62 public:
63 // ResourceHashtable is passed to various functions and populated in
64 // different places so we allocate it using C_HEAP to make it immune
65 // from any ResourceMarks that happen to be in the code paths.
66 ObjectMonitorsHashtable() : _ptrs(new (mtThread) PtrTable), _key_count(0), _om_count(0) {}
67
68 ~ObjectMonitorsHashtable();
69
70 void add_entry(void* key, ObjectMonitor* om);
71
72 void add_entry(void* key, PtrList* list) {
73 _ptrs->put(key, list);
74 _key_count++;
75 }
76
77 PtrList* get_entry(void* key) {
78 PtrList** listpp = _ptrs->get(key);
79 return (listpp == nullptr) ? nullptr : *listpp;
80 }
81
82 bool has_entry(void* key, ObjectMonitor* om);
83
84 size_t key_count() { return _key_count; }
85 size_t om_count() { return _om_count; }
86 };
87
88 class MonitorList {
89 friend class VMStructs;
90
91 private:
92 ObjectMonitor* volatile _head;
93 volatile size_t _count;
94 volatile size_t _max;
95
96 public:
97 void add(ObjectMonitor* monitor);
98 size_t unlink_deflated(Thread* current, LogStream* ls, elapsedTimer* timer_p,
99 GrowableArray<ObjectMonitor*>* unlinked_list);
100 size_t count() const;
101 size_t max() const;
102
103 class Iterator;
104 Iterator iterator() const;
105 };
106
107 class MonitorList::Iterator {
108 ObjectMonitor* _current;
109
110 public:
111 Iterator(ObjectMonitor* head) : _current(head) {}
112 bool has_next() const { return _current != nullptr; }
113 ObjectMonitor* next();
114 };
115
116 class ObjectSynchronizer : AllStatic {
117 friend class VMStructs;
118
119 public:
120 typedef enum {
121 inflate_cause_vm_internal = 0,
122 inflate_cause_monitor_enter = 1,
123 inflate_cause_wait = 2,
124 inflate_cause_notify = 3,
125 inflate_cause_hash_code = 4,
126 inflate_cause_jni_enter = 5,
127 inflate_cause_jni_exit = 6,
128 inflate_cause_nof = 7 // Number of causes
129 } InflateCause;
130
131 typedef enum {
132 NOT_ENABLED = 0,
133 FATAL_EXIT = 1,
134 LOG_WARNING = 2
135 } SyncDiagnosticOption;
136
137 // exit must be implemented non-blocking, since the compiler cannot easily handle
138 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
139
140 // This is the "slow path" version of monitor enter and exit.
141 static void enter(Handle obj, BasicLock* lock, JavaThread* current);
142 static void exit(oop obj, BasicLock* lock, JavaThread* current);
143 // Used to enter a monitor for another thread. This requires that the
144 // locking_thread is suspended, and that entering on a potential
145 // inflated monitor may only contend with deflation. That is the obj being
146 // locked on is either already locked by the locking_thread or cannot
147 // escape the locking_thread.
148 static void enter_for(Handle obj, BasicLock* lock, JavaThread* locking_thread);
149 private:
150 // Shared implementation for enter and enter_for. Performs all but
151 // inflated monitor enter.
152 static bool enter_fast_impl(Handle obj, BasicLock* lock, JavaThread* locking_thread);
153
154 public:
155 // Used only to handle jni locks or other unmatched monitor enter/exit
156 // Internally they will use heavy weight monitor.
157 static void jni_enter(Handle obj, JavaThread* current);
158 static void jni_exit(oop obj, TRAPS);
159
160 // Handle all interpreter, compiler and jni cases
161 static int wait(Handle obj, jlong millis, TRAPS);
162 static void notify(Handle obj, TRAPS);
163 static void notifyall(Handle obj, TRAPS);
164
165 static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
166 static bool quick_enter(oop obj, JavaThread* current, BasicLock* Lock);
167
168 // Inflate light weight monitor to heavy weight monitor
169 static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
170 // Used to inflate a monitor as if it was done from the thread JavaThread.
171 static ObjectMonitor* inflate_for(JavaThread* thread, oop obj, const InflateCause cause);
172
173 private:
174 // Shared implementation between the different LockingMode.
175 static ObjectMonitor* inflate_impl(JavaThread* thread, oop obj, const InflateCause cause);
176
177 public:
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 FastHashCode(Thread* current, oop obj);
185
186 // java.lang.Thread support
187 static bool current_thread_holds_lock(JavaThread* current, Handle h_obj);
188
189 static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
190
191 // JNI detach support
192 static void release_monitors_owned_by_thread(JavaThread* current);
193
194 // Iterate ObjectMonitors where the owner == thread; this does NOT include
195 // ObjectMonitors where owner is set to a stack lock address in thread:
196 //
197 // This version of monitors_iterate() works with the in-use monitor list.
198 static void monitors_iterate(MonitorClosure* m, JavaThread* thread);
199 // This version of monitors_iterate() works with the specified linked list.
200 static void monitors_iterate(MonitorClosure* closure,
201 ObjectMonitorsHashtable::PtrList* list,
202 JavaThread* thread);
203
204 // Initialize the gInflationLocks
205 static void initialize();
206
207 // GC: we currently use aggressive monitor deflation policy
208 // Basically we try to deflate all monitors that are not busy.
209 static size_t deflate_idle_monitors(ObjectMonitorsHashtable* table);
210
211 // Deflate idle monitors:
212 static void chk_for_block_req(JavaThread* current, const char* op_name,
213 const char* cnt_name, size_t cnt, LogStream* ls,
214 elapsedTimer* timer_p);
215 static size_t deflate_monitor_list(Thread* current, LogStream* ls, elapsedTimer* timer_p,
216 ObjectMonitorsHashtable* table);
217 static size_t in_use_list_ceiling();
218 static void dec_in_use_list_ceiling();
219 static void inc_in_use_list_ceiling();
220 static void set_in_use_list_ceiling(size_t new_value);
221 static bool is_async_deflation_needed();
222 static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
223 static bool is_final_audit() { return _is_final_audit; }
224 static void set_is_final_audit() { _is_final_audit = true; }
225 static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
226 static bool request_deflate_idle_monitors(); // for whitebox test support
227 static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
228 static jlong time_since_last_async_deflation_ms();
229
230 // debugging
231 static void audit_and_print_stats(bool on_exit);
232 static void chk_in_use_list(outputStream* out, int* error_cnt_p);
233 static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
234 int* error_cnt_p);
235 static void do_final_audit_and_print_stats();
236 static void log_in_use_monitor_details(outputStream* out);
237
238 private:
239 friend class SynchronizerTest;
240
241 static MonitorList _in_use_list;
242 static volatile bool _is_async_deflation_requested;
243 static volatile bool _is_final_audit;
244 static jlong _last_async_deflation_time_ns;
245
246 // Support for SynchronizerTest access to GVars fields:
247 static u_char* get_gvars_addr();
248 static u_char* get_gvars_hc_sequence_addr();
249 static size_t get_gvars_size();
250 static u_char* get_gvars_stw_random_addr();
251
252 static void handle_sync_on_value_based_class(Handle obj, JavaThread* locking_thread);
253 };
254
255 // ObjectLocker enforces balanced locking and can never throw an
256 // IllegalMonitorStateException. However, a pending exception may
257 // have to pass through, and we must also be able to deal with
258 // asynchronous exceptions. The caller is responsible for checking
259 // the thread's pending exception if needed.
260 class ObjectLocker : public StackObj {
261 private:
262 JavaThread* _thread;
263 Handle _obj;
264 BasicLock _lock;
265 public:
266 ObjectLocker(Handle obj, JavaThread* current);
267 ~ObjectLocker();
268
269 // Monitor behavior
270 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
271 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
272 };
273
274 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP