1  /* Default read-write lock implementation struct definitions.
       2     Copyright (C) 2019-2023 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  
      29  struct __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