1 /*
2 * Copyright (c) 1998, 2017, 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_VM_RUNTIME_SYNCHRONIZER_HPP
26 #define SHARE_VM_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
36 struct DeflateMonitorCounters {
37 int nInuse; // currently associated with objects
38 int nInCirculation; // extant
39 int nScavenged; // reclaimed
40 };
41
42 class ObjectSynchronizer : AllStatic {
43 friend class VMStructs;
44 public:
45 typedef enum {
46 owner_self,
47 owner_none,
48 owner_other
49 } LockOwnership;
50
51 typedef enum {
52 inflate_cause_vm_internal = 0,
53 inflate_cause_monitor_enter = 1,
54 inflate_cause_wait = 2,
55 inflate_cause_notify = 3,
56 inflate_cause_hash_code = 4,
57 inflate_cause_jni_enter = 5,
58 inflate_cause_jni_exit = 6,
59 inflate_cause_nof = 7 // Number of causes
60 } InflateCause;
61
62 // exit must be implemented non-blocking, since the compiler cannot easily handle
63 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
64
65 // This is full version of monitor enter and exit. I choose not
66 // to use enter() and exit() in order to make sure user be ware
67 // of the performance and semantics difference. They are normally
68 // used by ObjectLocker etc. The interpreter and compiler use
69 // assembly copies of these routines. Please keep them synchronized.
70 //
71 // attempt_rebias flag is used by UseBiasedLocking implementation
72 static void fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias,
73 TRAPS);
74 static void fast_exit(oop obj, BasicLock* lock, Thread* THREAD);
75
76 // WARNING: They are ONLY used to handle the slow cases. They should
77 // only be used when the fast cases failed. Use of these functions
78 // without previous fast case check may cause fatal error.
79 static void slow_enter(Handle obj, BasicLock* lock, TRAPS);
80 static void slow_exit(oop obj, BasicLock* lock, Thread* THREAD);
81
82 // Used only to handle jni locks or other unmatched monitor enter/exit
83 // Internally they will use heavy weight monitor.
84 static void jni_enter(Handle obj, TRAPS);
85 static void jni_exit(oop obj, Thread* THREAD);
86
87 // Handle all interpreter, compiler and jni cases
88 static int wait(Handle obj, jlong millis, TRAPS);
89 static void notify(Handle obj, TRAPS);
90 static void notifyall(Handle obj, TRAPS);
91
92 static bool quick_notify(oopDesc* obj, Thread* Self, bool All);
93 static bool quick_enter(oop obj, Thread* Self, BasicLock* Lock);
94
95 // Special internal-use-only method for use by JVM infrastructure
96 // that needs to wait() on a java-level object but that can't risk
97 // throwing unexpected InterruptedExecutionExceptions.
98 static void waitUninterruptibly(Handle obj, jlong Millis, Thread * THREAD);
99
100 // used by classloading to free classloader object lock,
101 // wait on an internal lock, and reclaim original lock
102 // with original recursion count
103 static intptr_t complete_exit(Handle obj, TRAPS);
104 static void reenter (Handle obj, intptr_t recursion, TRAPS);
105
106 // thread-specific and global objectMonitor free list accessors
107 static void verifyInUse(Thread * Self);
108 static ObjectMonitor * omAlloc(Thread * Self);
109 static void omRelease(Thread * Self, ObjectMonitor * m,
110 bool FromPerThreadAlloc);
111 static void omFlush(Thread * Self);
112
113 // Inflate light weight monitor to heavy weight monitor
114 static ObjectMonitor* inflate(Thread * Self, oop obj, const InflateCause cause);
115 // This version is only for internal use
116 static ObjectMonitor* inflate_helper(oop obj);
117 static const char* inflate_cause_name(const InflateCause cause);
118
119 // Returns the identity hash value for an oop
120 // NOTE: It may cause monitor inflation
121 static intptr_t identity_hash_value_for(Handle obj);
122 static intptr_t FastHashCode(Thread * Self, oop obj);
123
124 // java.lang.Thread support
125 static bool current_thread_holds_lock(JavaThread* thread, Handle h_obj);
126 static LockOwnership query_lock_ownership(JavaThread * self, Handle h_obj);
127
128 static JavaThread* get_lock_owner(Handle h_obj, bool doLock);
129
130 // JNI detach support
131 static void release_monitors_owned_by_thread(TRAPS);
132 static void monitors_iterate(MonitorClosure* m);
133
134 // GC: we current use aggressive monitor deflation policy
135 // Basically we deflate all monitors that are not busy.
136 // An adaptive profile-based deflation policy could be used if needed
137 static void deflate_idle_monitors(DeflateMonitorCounters* counters);
138 static void deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters);
139 static void prepare_deflate_idle_monitors(DeflateMonitorCounters* counters);
140 static void finish_deflate_idle_monitors(DeflateMonitorCounters* counters);
141
142 // For a given monitor list: global or per-thread, deflate idle monitors
143 static int deflate_monitor_list(ObjectMonitor** listheadp,
144 ObjectMonitor** freeHeadp,
145 ObjectMonitor** freeTailp);
146 static bool deflate_monitor(ObjectMonitor* mid, oop obj,
147 ObjectMonitor** freeHeadp,
148 ObjectMonitor** freeTailp);
149 static bool is_cleanup_needed();
150 static void oops_do(OopClosure* f);
151 // Process oops in thread local used monitors
152 static void thread_local_used_oops_do(Thread* thread, OopClosure* f);
153
154 // debugging
155 static void sanity_checks(const bool verbose,
156 const unsigned int cache_line_size,
157 int *error_cnt_ptr, int *warning_cnt_ptr);
158 static int verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;
159
160 private:
161 enum { _BLOCKSIZE = 128 };
162 // global list of blocks of monitors
163 static PaddedEnd<ObjectMonitor> * volatile gBlockList;
164 // global monitor free list
165 static ObjectMonitor * volatile gFreeList;
166 // global monitor in-use list, for moribund threads,
167 // monitors they inflated need to be scanned for deflation
168 static ObjectMonitor * volatile gOmInUseList;
169 // count of entries in gOmInUseList
170 static int gOmInUseCount;
171
172 // Process oops in all monitors
173 static void global_oops_do(OopClosure* f);
174 // Process oops in all global used monitors (i.e. moribund thread's monitors)
175 static void global_used_oops_do(OopClosure* f);
176 // Process oops in monitors on the given list
177 static void list_oops_do(ObjectMonitor* list, OopClosure* f);
178
179 };
180
181 // ObjectLocker enforced balanced locking and can never thrown an
182 // IllegalMonitorStateException. However, a pending exception may
183 // have to pass through, and we must also be able to deal with
184 // asynchronous exceptions. The caller is responsible for checking
185 // the threads pending exception if needed.
186 // doLock was added to support classloading with UnsyncloadClass which
187 // requires flag based choice of locking the classloader lock.
188 class ObjectLocker : public StackObj {
189 private:
190 Thread* _thread;
191 Handle _obj;
192 BasicLock _lock;
193 bool _dolock; // default true
194 public:
195 ObjectLocker(Handle obj, Thread* thread, bool doLock = true);
196 ~ObjectLocker();
197
198 // Monitor behavior
199 void wait(TRAPS) { ObjectSynchronizer::wait(_obj, 0, CHECK); } // wait forever
200 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
201 void waitUninterruptibly(TRAPS) { ObjectSynchronizer::waitUninterruptibly(_obj, 0, CHECK); }
202 // complete_exit gives up lock completely, returning recursion count
203 // reenter reclaims lock with original recursion count
204 intptr_t complete_exit(TRAPS) { return ObjectSynchronizer::complete_exit(_obj, THREAD); }
205 void reenter(intptr_t recursion, TRAPS) { ObjectSynchronizer::reenter(_obj, recursion, CHECK); }
206 };
207
208 #endif // SHARE_VM_RUNTIME_SYNCHRONIZER_HPP