1 /*
2 * Copyright (c) 1998, 2019, 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 *
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 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/markOop.hpp"
30 #include "runtime/basicLock.hpp"
31 #include "runtime/handles.hpp"
32 #include "runtime/perfData.hpp"
33
34 class ObjectMonitor;
35 class ThreadsList;
36
37 struct DeflateMonitorCounters {
38 int nInuse; // currently associated with objects
39 int nInCirculation; // extant
40 int nScavenged; // reclaimed (global and per-thread)
41 int perThreadScavenged; // per-thread scavenge total
42 double perThreadTimes; // per-thread scavenge times
43 };
44
45 class ObjectSynchronizer : AllStatic {
46 friend class VMStructs;
47 public:
48 typedef enum {
49 owner_self,
50 owner_none,
51 owner_other
52 } LockOwnership;
53
54 typedef enum {
55 inflate_cause_vm_internal = 0,
56 inflate_cause_monitor_enter = 1,
57 inflate_cause_wait = 2,
58 inflate_cause_notify = 3,
59 inflate_cause_hash_code = 4,
60 inflate_cause_jni_enter = 5,
61 inflate_cause_jni_exit = 6,
62 inflate_cause_nof = 7 // Number of causes
63 } InflateCause;
64
65 // exit must be implemented non-blocking, since the compiler cannot easily handle
66 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
67
68 // This is full version of monitor enter and exit. I choose not
69 // to use enter() and exit() in order to make sure user be ware
70 // of the performance and semantics difference. They are normally
71 // used by ObjectLocker etc. The interpreter and compiler use
72 // assembly copies of these routines. Please keep them synchronized.
73 //
74 // attempt_rebias flag is used by UseBiasedLocking implementation
75 static void fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias,
76 TRAPS);
77 static void fast_exit(oop obj, BasicLock* lock, Thread* THREAD);
78
79 // WARNING: They are ONLY used to handle the slow cases. They should
80 // only be used when the fast cases failed. Use of these functions
81 // without previous fast case check may cause fatal error.
82 static void slow_enter(Handle obj, BasicLock* lock, TRAPS);
83 static void slow_exit(oop obj, BasicLock* lock, Thread* THREAD);
84
85 // Used only to handle jni locks or other unmatched monitor enter/exit
86 // Internally they will use heavy weight monitor.
87 static void jni_enter(Handle obj, TRAPS);
88 static void jni_exit(oop obj, Thread* THREAD);
89
90 // Handle all interpreter, compiler and jni cases
91 static int wait(Handle obj, jlong millis, TRAPS);
92 static void notify(Handle obj, TRAPS);
93 static void notifyall(Handle obj, TRAPS);
94
95 static bool quick_notify(oopDesc* obj, Thread* Self, bool All);
96 static bool quick_enter(oop obj, Thread* Self, BasicLock* Lock);
97
98 // Special internal-use-only method for use by JVM infrastructure
99 // that needs to wait() on a java-level object but that can't risk
100 // throwing unexpected InterruptedExecutionExceptions.
101 static void waitUninterruptibly(Handle obj, jlong Millis, Thread * THREAD);
102
103 // used by classloading to free classloader object lock,
104 // wait on an internal lock, and reclaim original lock
105 // with original recursion count
106 static intptr_t complete_exit(Handle obj, TRAPS);
107 static void reenter (Handle obj, intptr_t recursion, TRAPS);
108
109 // thread-specific and global objectMonitor free list accessors
110 static ObjectMonitor * omAlloc(Thread * Self);
111 static void omRelease(Thread * Self, ObjectMonitor * m,
112 bool FromPerThreadAlloc);
113 static void omFlush(Thread * Self);
114
115 // Inflate light weight monitor to heavy weight monitor
116 static ObjectMonitor* inflate(Thread * Self, oop obj, const InflateCause cause);
117 // This version is only for internal use
118 static void inflate_helper(oop obj);
119 static const char* inflate_cause_name(const InflateCause cause);
120
121 // Returns the identity hash value for an oop
122 // NOTE: It may cause monitor inflation
123 static intptr_t identity_hash_value_for(Handle obj);
124 static intptr_t FastHashCode(Thread * Self, oop obj);
125
126 // java.lang.Thread support
127 static bool current_thread_holds_lock(JavaThread* thread, Handle h_obj);
128 static LockOwnership query_lock_ownership(JavaThread * self, Handle h_obj);
129
130 static JavaThread* get_lock_owner(ThreadsList * t_list, Handle h_obj);
131
132 // JNI detach support
133 static void release_monitors_owned_by_thread(TRAPS);
134 static void monitors_iterate(MonitorClosure* m);
135
136 // GC: we current use aggressive monitor deflation policy
137 // Basically we deflate all monitors that are not busy.
138 // An adaptive profile-based deflation policy could be used if needed
139 static void deflate_idle_monitors(DeflateMonitorCounters* counters);
140 static void deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters);
141 static void prepare_deflate_idle_monitors(DeflateMonitorCounters* counters);
142 static void finish_deflate_idle_monitors(DeflateMonitorCounters* counters);
143
144 // For a given monitor list: global or per-thread, deflate idle monitors
145 static int deflate_monitor_list(ObjectMonitor** listheadp,
146 ObjectMonitor** freeHeadp,
147 ObjectMonitor** freeTailp);
148 static bool deflate_monitor(ObjectMonitor* mid, oop obj,
149 ObjectMonitor** freeHeadp,
150 ObjectMonitor** freeTailp);
151 static bool is_cleanup_needed();
152 static void oops_do(OopClosure* f);
153 // Process oops in thread local used monitors
154 static void thread_local_used_oops_do(Thread* thread, OopClosure* f);
155
156 // debugging
157 static void audit_and_print_stats(bool on_exit);
158 static void chk_free_entry(JavaThread * jt, ObjectMonitor * n,
159 outputStream * out, int *error_cnt_p);
160 static void chk_global_free_list_and_count(outputStream * out,
161 int *error_cnt_p);
162 static void chk_global_in_use_list_and_count(outputStream * out,
163 int *error_cnt_p);
164 static void chk_in_use_entry(JavaThread * jt, ObjectMonitor * n,
165 outputStream * out, int *error_cnt_p);
166 static void chk_per_thread_in_use_list_and_count(JavaThread *jt,
167 outputStream * out,
168 int *error_cnt_p);
169 static void chk_per_thread_free_list_and_count(JavaThread *jt,
170 outputStream * out,
171 int *error_cnt_p);
172 static void log_in_use_monitor_details(outputStream * out, bool on_exit);
173 static int log_monitor_list_counts(outputStream * out);
174 static int verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;
175
176 private:
177 friend class SynchronizerTest;
178
179 enum { _BLOCKSIZE = 128 };
180 // global list of blocks of monitors
181 static PaddedEnd<ObjectMonitor> * volatile gBlockList;
182 // global monitor free list
183 static ObjectMonitor * volatile gFreeList;
184 // global monitor in-use list, for moribund threads,
185 // monitors they inflated need to be scanned for deflation
186 static ObjectMonitor * volatile gOmInUseList;
187 // count of entries in gOmInUseList
188 static int gOmInUseCount;
189
190 // Process oops in all global used monitors (i.e. moribund thread's monitors)
191 static void global_used_oops_do(OopClosure* f);
192 // Process oops in monitors on the given list
193 static void list_oops_do(ObjectMonitor* list, OopClosure* f);
194
195 // Support for SynchronizerTest access to GVars fields:
196 static u_char* get_gvars_addr();
197 static u_char* get_gvars_hcSequence_addr();
198 static size_t get_gvars_size();
199 static u_char* get_gvars_stwRandom_addr();
200 };
201
202 // ObjectLocker enforces balanced locking and can never throw an
203 // IllegalMonitorStateException. However, a pending exception may
204 // have to pass through, and we must also be able to deal with
205 // asynchronous exceptions. The caller is responsible for checking
206 // the thread's pending exception if needed.
207 class ObjectLocker : public StackObj {
208 private:
209 Thread* _thread;
210 Handle _obj;
211 BasicLock _lock;
212 bool _dolock; // default true
213 public:
214 ObjectLocker(Handle obj, Thread* thread, bool doLock = true);
215 ~ObjectLocker();
216
217 // Monitor behavior
218 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
219 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
220 void waitUninterruptibly(TRAPS) { ObjectSynchronizer::waitUninterruptibly(_obj, 0, CHECK); }
221 // complete_exit gives up lock completely, returning recursion count
222 // reenter reclaims lock with original recursion count
223 intptr_t complete_exit(TRAPS) { return ObjectSynchronizer::complete_exit(_obj, THREAD); }
224 void reenter(intptr_t recursion, TRAPS) { ObjectSynchronizer::reenter(_obj, recursion, CHECK); }
225 };
226
227 #endif // SHARE_RUNTIME_SYNCHRONIZER_HPP