1 /*
2 * Copyright (c) 1998, 2007, 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
26 class ObjectMonitor;
27
28 class ObjectSynchronizer : AllStatic {
29 friend class VMStructs;
30 public:
31 typedef enum {
32 owner_self,
33 owner_none,
34 owner_other
35 } LockOwnership;
36 // exit must be implemented non-blocking, since the compiler cannot easily handle
37 // deoptimization at monitor exit. Hence, it does not take a Handle argument.
38
39 // This is full version of monitor enter and exit. I choose not
40 // to use enter() and exit() in order to make sure user be ware
41 // of the performance and semantics difference. They are normally
42 // used by ObjectLocker etc. The interpreter and compiler use
43 // assembly copies of these routines. Please keep them synchornized.
44 //
45 // attempt_rebias flag is used by UseBiasedLocking implementation
46 static void fast_enter (Handle obj, BasicLock* lock, bool attempt_rebias, TRAPS);
47 static void fast_exit (oop obj, BasicLock* lock, Thread* THREAD);
48
49 // WARNING: They are ONLY used to handle the slow cases. They should
50 // only be used when the fast cases failed. Use of these functions
51 // without previous fast case check may cause fatal error.
52 static void slow_enter (Handle obj, BasicLock* lock, TRAPS);
53 static void slow_exit (oop obj, BasicLock* lock, Thread* THREAD);
54
55 // Used only to handle jni locks or other unmatched monitor enter/exit
56 // Internally they will use heavy weight monitor.
57 static void jni_enter (Handle obj, TRAPS);
58 static bool jni_try_enter(Handle obj, Thread* THREAD); // Implements Unsafe.tryMonitorEnter
59 static void jni_exit (oop obj, Thread* THREAD);
60
61 // Handle all interpreter, compiler and jni cases
62 static void wait (Handle obj, jlong millis, TRAPS);
63 static void notify (Handle obj, TRAPS);
64 static void notifyall (Handle obj, TRAPS);
65
66 // Special internal-use-only method for use by JVM infrastructure
67 // that needs to wait() on a java-level object but that can't risk
68 // throwing unexpected InterruptedExecutionExceptions.
69 static void waitUninterruptibly (Handle obj, jlong Millis, Thread * THREAD) ;
70
71 // used by classloading to free classloader object lock,
72 // wait on an internal lock, and reclaim original lock
73 // with original recursion count
74 static intptr_t complete_exit (Handle obj, TRAPS);
75 static void reenter (Handle obj, intptr_t recursion, TRAPS);
76
77 // thread-specific and global objectMonitor free list accessors
78 // static void verifyInUse (Thread * Self) ; too slow for general assert/debug
79 static ObjectMonitor * omAlloc (Thread * Self) ;
80 static void omRelease (Thread * Self, ObjectMonitor * m, bool FromPerThreadAlloc) ;
81 static void omFlush (Thread * Self) ;
82
83 // Inflate light weight monitor to heavy weight monitor
84 static ObjectMonitor* inflate(Thread * Self, oop obj);
85 // This version is only for internal use
86 static ObjectMonitor* inflate_helper(oop obj);
87
88 // Returns the identity hash value for an oop
89 // NOTE: It may cause monitor inflation
90 static intptr_t identity_hash_value_for(Handle obj);
91 static intptr_t FastHashCode (Thread * Self, oop obj) ;
92
93 // java.lang.Thread support
94 static bool current_thread_holds_lock(JavaThread* thread, Handle h_obj);
95 static LockOwnership query_lock_ownership(JavaThread * self, Handle h_obj);
96
97 static JavaThread* get_lock_owner(Handle h_obj, bool doLock);
98
99 // JNI detach support
100 static void release_monitors_owned_by_thread(TRAPS);
101 static void monitors_iterate(MonitorClosure* m);
102
103 // GC: we current use aggressive monitor deflation policy
104 // Basically we deflate all monitors that are not busy.
105 // An adaptive profile-based deflation policy could be used if needed
106 static void deflate_idle_monitors();
107 static int walk_monitor_list(ObjectMonitor** listheadp,
108 ObjectMonitor** FreeHeadp,
109 ObjectMonitor** FreeTailp);
110 static bool deflate_monitor(ObjectMonitor* mid, oop obj, ObjectMonitor** FreeHeadp,
111 ObjectMonitor** FreeTailp);
112 static void oops_do(OopClosure* f);
113
114 // debugging
115 static void trace_locking(Handle obj, bool is_compiled, bool is_method, bool is_locking) PRODUCT_RETURN;
116 static void verify() PRODUCT_RETURN;
117 static int verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;
118
119 static void RegisterSpinCallback (int (*)(intptr_t, int), intptr_t) ;
120
121 private:
122 enum { _BLOCKSIZE = 128 };
123 static ObjectMonitor* gBlockList;
124 static ObjectMonitor * volatile gFreeList;
125 static ObjectMonitor * volatile gOmInUseList; // for moribund thread, so monitors they inflated still get scanned
126 static int gOmInUseCount;
127
128 };
129
130 // ObjectLocker enforced balanced locking and can never thrown an
131 // IllegalMonitorStateException. However, a pending exception may
132 // have to pass through, and we must also be able to deal with
133 // asynchronous exceptions. The caller is responsible for checking
134 // the threads pending exception if needed.
135 // doLock was added to support classloading with UnsyncloadClass which
136 // requires flag based choice of locking the classloader lock.
137 class ObjectLocker : public StackObj {
138 private:
139 Thread* _thread;
140 Handle _obj;
141 BasicLock _lock;
142 bool _dolock; // default true
143 public:
144 ObjectLocker(Handle obj, Thread* thread, bool doLock = true);
145 ~ObjectLocker();
146
147 // Monitor behavior
148 void wait (TRAPS) { ObjectSynchronizer::wait (_obj, 0, CHECK); } // wait forever
149 void notify_all(TRAPS) { ObjectSynchronizer::notifyall(_obj, CHECK); }
150 void waitUninterruptibly (TRAPS) { ObjectSynchronizer::waitUninterruptibly (_obj, 0, CHECK);}
151 // complete_exit gives up lock completely, returning recursion count
152 // reenter reclaims lock with original recursion count
153 intptr_t complete_exit(TRAPS) { return ObjectSynchronizer::complete_exit(_obj, CHECK_0); }
154 void reenter(intptr_t recursion, TRAPS) { ObjectSynchronizer::reenter(_obj, recursion, CHECK); }
155 };