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.
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23 */
24
25 #ifndef SHARE_RUNTIME_BASICLOCK_HPP
26 #define SHARE_RUNTIME_BASICLOCK_HPP
27
28 #include "oops/markWord.hpp"
29 #include "runtime/atomic.hpp"
30 #include "runtime/handles.hpp"
31 #include "utilities/globalDefinitions.hpp"
32 #include "utilities/sizes.hpp"
33
34 class BasicLock {
35 friend class VMStructs;
36 friend class JVMCIVMStructs;
37 private:
38 // * For LM_MONITOR
39 // Unused.
40 // * For LM_LEGACY
41 // This is either the actual displaced header from a locked object, or
42 // a sentinel zero value indicating a recursive stack-lock.
43 // * For LM_LIGHTWEIGHT
44 // Used as a cache the ObjectMonitor* used when locking. Must either
45 // be nullptr or the ObjectMonitor* used when locking.
46 volatile uintptr_t _metadata;
47
48 uintptr_t get_metadata() const { return Atomic::load(&_metadata); }
49 void set_metadata(uintptr_t value) { Atomic::store(&_metadata, value); }
50 static int metadata_offset_in_bytes() { return (int)offset_of(BasicLock, _metadata); }
51
52 public:
53 // LM_MONITOR
54 void set_bad_metadata_deopt() { set_metadata(badDispHeaderDeopt); }
55
56 // LM_LEGACY
57 inline markWord displaced_header() const;
58 inline void set_displaced_header(markWord header);
59 static int displaced_header_offset_in_bytes() { return metadata_offset_in_bytes(); }
60
61 // LM_LIGHTWEIGHT
62 inline ObjectMonitor* object_monitor_cache() const;
63 inline void clear_object_monitor_cache();
64 inline void set_object_monitor_cache(ObjectMonitor* mon);
65 static int object_monitor_cache_offset_in_bytes() { return metadata_offset_in_bytes(); }
66
67 void print_on(outputStream* st, oop owner) const;
68
69 // move a basic lock (used during deoptimization)
70 void move_to(oop obj, BasicLock* dest);
71 };
72
73 // A BasicObjectLock associates a specific Java object with a BasicLock.
74 // It is currently embedded in an interpreter frame.
75
76 // Because some machines have alignment restrictions on the control stack,
77 // the actual space allocated by the interpreter may include padding words
78 // after the end of the BasicObjectLock. Also, in order to guarantee
79 // alignment of the embedded BasicLock objects on such machines, we
80 // put the embedded BasicLock at the beginning of the struct.
81
82 class BasicObjectLock {
83 friend class VMStructs;
84 private:
85 BasicLock _lock; // the lock, must be double word aligned
86 oop _obj; // object holds the lock;
87
88 public:
89 // Manipulation
90 oop obj() const { return _obj; }
91 void set_obj(oop obj) { _obj = obj; }
92 BasicLock* lock() { return &_lock; }
93
94 // Note: Use frame::interpreter_frame_monitor_size() for the size of BasicObjectLocks
95 // in interpreter activation frames since it includes machine-specific padding.
96 static int size() { return sizeof(BasicObjectLock)/wordSize; }
97
98 // GC support
99 void oops_do(OopClosure* f) { f->do_oop(&_obj); }
100
101 static ByteSize obj_offset() { return byte_offset_of(BasicObjectLock, _obj); }
102 static ByteSize lock_offset() { return byte_offset_of(BasicObjectLock, _lock); }
103 };
104
105
106 #endif // SHARE_RUNTIME_BASICLOCK_HPP