1/* Default read-write lock implementation struct definitions.
 2   Copyright (C) 2019-2025 Free Software Foundation, Inc.
 3   This file is part of the GNU C Library.
 4
 5   The GNU C Library is free software; you can redistribute it and/or
 6   modify it under the terms of the GNU Lesser General Public
 7   License as published by the Free Software Foundation; either
 8   version 2.1 of the License, or (at your option) any later version.
 9
10   The GNU C Library is distributed in the hope that it will be useful,
11   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   Lesser General Public License for more details.
14
15   You should have received a copy of the GNU Lesser General Public
16   License along with the GNU C Library; if not, see
17   <http://www.gnu.org/licenses/>.  */
18
19#ifndef __RWLOCK_INTERNAL_H
20#define __RWLOCK_INTERNAL_H
21
22#include <bits/endian.h>
23
24/* Generic struct for both POSIX read-write lock.  New ports are expected
25   to use the default layout, however archictetures can redefine it to add
26   arch-specific extensions (such as lock-elision).  The struct have a size
27   of 32 bytes on both LP32 and LP64 architectures.  */
28
29struct __pthread_rwlock_arch_t
30{
31  unsigned int __readers;
32  unsigned int __writers;
33  unsigned int __wrphase_futex;
34  unsigned int __writers_futex;
35  unsigned int __pad3;
36  unsigned int __pad4;
37  /* FLAGS must stay at its position in the structure to maintain
38     binary compatibility.  */
39#if __BYTE_ORDER == __BIG_ENDIAN
40  unsigned char __pad1;
41  unsigned char __pad2;
42  unsigned char __shared;
43  unsigned char __flags;
44#else
45  unsigned char __flags;
46  unsigned char __shared;
47  unsigned char __pad1;
48  unsigned char __pad2;
49#endif
50  int __cur_writer;
51};
52
53#if __BYTE_ORDER == __BIG_ENDIAN
54# define __PTHREAD_RWLOCK_INITIALIZER(__flags) \
55  0, 0, 0, 0, 0, 0, 0, 0, 0, __flags, 0
56#else
57# define __PTHREAD_RWLOCK_INITIALIZER(__flags) \
58  0, 0, 0, 0, 0, 0, __flags, 0, 0, 0, 0
59#endif
60
61#endif