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  *
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  *
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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 
32 // A BasicObjectLock represents a locked object.
33 // It is currently embedded in an interpreter frame.
34 
35 // Because some machines have alignment restrictions on the control stack,
36 // the actual space allocated by the interpreter may include padding words
37 // after the end of the BasicObjectLock.
38 
39 class BasicObjectLock {
40   friend class VMStructs;
41  private:
42   oop       _obj;                                     // object holds the lock;
43 #if defined(AARCH64) || defined(RISCV64)
44   // Stack needs to be 16-byte-aligned. Inserting a dummy field here is
45   // the simplest way to achieve that.
46   intptr_t _dummy;
47 #endif
48 
49  public:
50   // Manipulation
51   oop      obj() const                                { return _obj;  }
52   void set_obj(oop obj)                               { _obj = obj; }
53 
54   // Note: Use frame::interpreter_frame_monitor_size() for the size of BasicObjectLocks
55   //       in interpreter activation frames since it includes machine-specific padding.
56   static int size()                                   { return sizeof(BasicObjectLock)/wordSize; }
57 
58   // GC support
59   void oops_do(OopClosure* f) { f->do_oop(&_obj); }
60 
61   static int obj_offset_in_bytes()                    { return offset_of(BasicObjectLock, _obj);  }
62 };
63 
64 
65 #endif // SHARE_RUNTIME_BASICLOCK_HPP