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
21 * questions.
22 *
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 class MonitorList {
40 friend class VMStructs;
41
42 private:
43 ObjectMonitor* volatile _head;
44 volatile size_t _count;
45 volatile size_t _max;
46
47 public:
48 void add(ObjectMonitor* monitor);
49 size_t unlink_deflated(Thread* current, LogStream* ls, elapsedTimer* timer_p,
50 size_t deflated_count,
51 GrowableArray<ObjectMonitor*>* unlinked_list);
52 size_t count() const;
53 size_t max() const;
54
55 class Iterator;
56 Iterator iterator() const;
57 };
58
59 class MonitorList::Iterator {
60 ObjectMonitor* _current;
61
62 public:
63 Iterator(ObjectMonitor* head) : _current(head) {}
64 bool has_next() const { return _current != nullptr; }
65 ObjectMonitor* next();
66 };
67
68 class ObjectSynchronizer : AllStatic {
69 friend class VMStructs;
70
71 public:
72 typedef enum {
73 inflate_cause_vm_internal = 0,
74 inflate_cause_monitor_enter = 1,
75 inflate_cause_wait = 2,
76 inflate_cause_notify = 3,
77 inflate_cause_hash_code = 4,
78 inflate_cause_jni_enter = 5,
79 inflate_cause_jni_exit = 6,
80 inflate_cause_nof = 7 // Number of causes
81 } InflateCause;
82
83 typedef enum {
84 NOT_ENABLED = 0,
85 FATAL_EXIT = 1,
86 LOG_WARNING = 2
87 } SyncDiagnosticOption;
88
89 // exit must be implemented non-blocking, since the compiler cannot easily handle
90 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
91
92 // This is the "slow path" version of monitor enter and exit.
93 static void enter(Handle obj, BasicLock* lock, JavaThread* current);
94 static void exit(oop obj, BasicLock* lock, JavaThread* current);
95 // Used to enter a monitor for another thread. This requires that the
96 // locking_thread is suspended, and that entering on a potential
97 // inflated monitor may only contend with deflation. That is the obj being
98 // locked on is either already locked by the locking_thread or cannot
99 // escape the locking_thread.
100 static void enter_for(Handle obj, BasicLock* lock, JavaThread* locking_thread);
101 private:
102 // Shared implementation for enter and enter_for. Performs all but
103 // inflated monitor enter.
104 static bool enter_fast_impl(Handle obj, BasicLock* lock, JavaThread* locking_thread);
105
106 public:
107 // Used only to handle jni locks or other unmatched monitor enter/exit
108 // Internally they will use heavy weight monitor.
109 static void jni_enter(Handle obj, JavaThread* current);
110 static void jni_exit(oop obj, TRAPS);
111
112 // Handle all interpreter, compiler and jni cases
113 static int wait(Handle obj, jlong millis, TRAPS);
114 static void notify(Handle obj, TRAPS);
115 static void notifyall(Handle obj, TRAPS);
116
117 static bool quick_notify(oopDesc* obj, JavaThread* current, bool All);
118 static bool quick_enter(oop obj, JavaThread* current, BasicLock* Lock);
119
120 // Special internal-use-only method for use by JVM infrastructure
121 // that needs to wait() on a java-level object but that can't risk
122 // throwing unexpected InterruptedExecutionExceptions.
123 static void waitUninterruptibly(Handle obj, jlong Millis, TRAPS);
124
125 // Inflate light weight monitor to heavy weight monitor
126 static ObjectMonitor* inflate(Thread* current, oop obj, const InflateCause cause);
127 // Used to inflate a monitor as if it was done from the thread JavaThread.
128 static ObjectMonitor* inflate_for(JavaThread* thread, oop obj, const InflateCause cause);
129
130 private:
131 // Shared implementation between the different LockingMode.
132 static ObjectMonitor* inflate_impl(JavaThread* thread, oop obj, const InflateCause cause);
133
134 public:
135 // This version is only for internal use
136 static void inflate_helper(oop obj);
137 static const char* inflate_cause_name(const InflateCause cause);
138
139 // Returns the identity hash value for an oop
140 // NOTE: It may cause monitor inflation
141 static intptr_t FastHashCode(Thread* current, oop obj);
142
143 // java.lang.Thread support
144 static bool current_thread_holds_lock(JavaThread* current, Handle h_obj);
145
146 static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
147
148 // JNI detach support
149 static void release_monitors_owned_by_thread(JavaThread* current);
150
151 // Iterate over all ObjectMonitors.
152 template <typename Function>
153 static void monitors_iterate(Function function);
154
155 // Iterate ObjectMonitors owned by any thread and where the owner `filter`
156 // returns true.
157 template <typename OwnerFilter>
158 static void owned_monitors_iterate_filtered(MonitorClosure* closure, OwnerFilter filter);
159
160 // Iterate ObjectMonitors where the owner == thread; this does NOT include
161 // ObjectMonitors where owner is set to a stack lock address in thread.
162 static void owned_monitors_iterate(MonitorClosure* m, JavaThread* thread);
163
164 // Iterate ObjectMonitors owned by any thread.
165 static void owned_monitors_iterate(MonitorClosure* closure);
166
167 // Initialize the gInflationLocks
168 static void initialize();
169
170 // We currently use aggressive monitor deflation policy;
171 // basically we try to deflate all monitors that are not busy.
172 static size_t deflate_idle_monitors();
173
174 // Deflate idle monitors:
175 static void chk_for_block_req(JavaThread* current, const char* op_name,
176 const char* cnt_name, size_t cnt, LogStream* ls,
177 elapsedTimer* timer_p);
178 static size_t deflate_monitor_list(Thread* current, LogStream* ls, elapsedTimer* timer_p);
179 static size_t in_use_list_ceiling();
180 static void dec_in_use_list_ceiling();
181 static void inc_in_use_list_ceiling();
182 static void set_in_use_list_ceiling(size_t new_value);
183 static bool is_async_deflation_needed();
184 static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
185 static bool is_final_audit() { return _is_final_audit; }
186 static void set_is_final_audit() { _is_final_audit = true; }
187 static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
188 static void request_deflate_idle_monitors();
189 static bool request_deflate_idle_monitors_from_wb(); // for whitebox test support
190 static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
191 static jlong time_since_last_async_deflation_ms();
192
193 // debugging
194 static void audit_and_print_stats(bool on_exit);
195 static void chk_in_use_list(outputStream* out, int* error_cnt_p);
196 static void chk_in_use_entry(ObjectMonitor* n, outputStream* out,
197 int* error_cnt_p);
198 static void do_final_audit_and_print_stats();
199 static void log_in_use_monitor_details(outputStream* out, bool log_all);
200
201 private:
202 friend class SynchronizerTest;
203
204 static MonitorList _in_use_list;
205 static volatile bool _is_async_deflation_requested;
206 static volatile bool _is_final_audit;
207 static jlong _last_async_deflation_time_ns;
208
209 // Support for SynchronizerTest access to GVars fields:
210 static u_char* get_gvars_addr();
211 static u_char* get_gvars_hc_sequence_addr();
212 static size_t get_gvars_size();
213 static u_char* get_gvars_stw_random_addr();
214
215 static void handle_sync_on_value_based_class(Handle obj, JavaThread* locking_thread);
216 };
217
218 // ObjectLocker enforces balanced locking and can never throw an
219 // IllegalMonitorStateException. However, a pending exception may
220 // have to pass through, and we must also be able to deal with
221 // asynchronous exceptions. The caller is responsible for checking
222 // the thread's pending exception if needed.
223 class ObjectLocker : public StackObj {
224 private:
225 JavaThread* _thread;
226 Handle _obj;
227 BasicLock _lock;
228 public:
229 ObjectLocker(Handle obj, JavaThread* current);
230 ~ObjectLocker();
231
232 // Monitor behavior
233 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
234 void wait_uninterruptibly(TRAPS) { ObjectSynchronizer::waitUninterruptibly(_obj, 0, CHECK); } // wait forever
235 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
236 };
237
238 // Interface to visit monitors
239 class ObjectMonitorsView {
240 public:
241 // Visit monitors that belong to the given thread
242 virtual void visit(MonitorClosure* closure, JavaThread* thread) = 0;
243 };
244
245 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP