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.
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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/sizes.hpp"
32
33 class BasicLock {
34 friend class VMStructs;
35 friend class JVMCIVMStructs;
36 private:
37 // This is either the actual displaced header from a locked object, or
38 // a sentinel zero value indicating a recursive stack-lock.
39 volatile markWord _displaced_header;
40 public:
41 markWord displaced_header() const {
42 return Atomic::load(&_displaced_header);
43 }
44
45 void set_displaced_header(markWord header) {
46 Atomic::store(&_displaced_header, header);
47 }
48
49 // TODO[OMWorld]: Cleanup these names, the storage `_displaced_header` usage depends on the locking mode.
50 void clear_displaced_header() {
51 Atomic::store(&_displaced_header, markWord(0));
52 }
53
54 void set_displaced_header(ObjectMonitor* mon) {
55 Atomic::store(&_displaced_header, markWord::from_pointer(mon));
56 }
57
58 void print_on(outputStream* st, oop owner) const;
59
60 // move a basic lock (used during deoptimization)
61 void move_to(oop obj, BasicLock* dest);
62
63 static int displaced_header_offset_in_bytes() { return (int)offset_of(BasicLock, _displaced_header); }
64 };
65
66 // A BasicObjectLock associates a specific Java object with a BasicLock.
67 // It is currently embedded in an interpreter frame.
68
69 // Because some machines have alignment restrictions on the control stack,
70 // the actual space allocated by the interpreter may include padding words
71 // after the end of the BasicObjectLock. Also, in order to guarantee
72 // alignment of the embedded BasicLock objects on such machines, we
73 // put the embedded BasicLock at the beginning of the struct.
74
75 class BasicObjectLock {
76 friend class VMStructs;
77 private:
78 BasicLock _lock; // the lock, must be double word aligned
79 oop _obj; // object holds the lock;
80
81 public:
82 // Manipulation
83 oop obj() const { return _obj; }
84 void set_obj(oop obj) { _obj = obj; }
85 BasicLock* lock() { return &_lock; }
86
87 // Note: Use frame::interpreter_frame_monitor_size() for the size of BasicObjectLocks
88 // in interpreter activation frames since it includes machine-specific padding.
89 static int size() { return sizeof(BasicObjectLock)/wordSize; }
90
91 // GC support
92 void oops_do(OopClosure* f) { f->do_oop(&_obj); }
93
94 static ByteSize obj_offset() { return byte_offset_of(BasicObjectLock, _obj); }
95 static ByteSize lock_offset() { return byte_offset_of(BasicObjectLock, _lock); }
96 };
97
98
99 #endif // SHARE_RUNTIME_BASICLOCK_HPP