1                 : // Support for atomic operations -*- C++ -*-
       2                 : 
       3                 : // Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
       4                 : //
       5                 : // This file is part of the GNU ISO C++ Library.  This library is free
       6                 : // software; you can redistribute it and/or modify it under the
       7                 : // terms of the GNU General Public License as published by the
       8                 : // Free Software Foundation; either version 2, or (at your option)
       9                 : // any later version.
      10                 : 
      11                 : // This library is distributed in the hope that it will be useful,
      12                 : // but WITHOUT ANY WARRANTY; without even the implied warranty of
      13                 : // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14                 : // GNU General Public License for more details.
      15                 : 
      16                 : // You should have received a copy of the GNU General Public License along
      17                 : // with this library; see the file COPYING.  If not, write to the Free
      18                 : // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
      19                 : // USA.
      20                 : 
      21                 : // As a special exception, you may use this file as part of a free software
      22                 : // library without restriction.  Specifically, if other files instantiate
      23                 : // templates or use macros or inline functions from this file, or you compile
      24                 : // this file and link it with other files to produce an executable, this
      25                 : // file does not by itself cause the resulting executable to be covered by
      26                 : // the GNU General Public License.  This exception does not however
      27                 : // invalidate any other reasons why the executable file might be covered by
      28                 : // the GNU General Public License.
      29                 : 
      30                 : /** @file atomicity.h
      31                 :  *  This is an internal header file, included by other library headers.
      32                 :  *  You should not attempt to use it directly.
      33                 :  */
      34                 : 
      35                 : #ifndef _GLIBCXX_ATOMICITY_H
      36                 : #define _GLIBCXX_ATOMICITY_H    1
      37                 : 
      38                 : #include <bits/c++config.h>
      39                 : #include <bits/gthr.h>
      40                 : #include <bits/atomic_word.h>
      41                 : 
      42                 : _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
      43                 : 
      44                 :   // Functions for portable atomic access.
      45                 :   // To abstract locking primatives across all thread policies, use:
      46                 :   // __exchange_and_add_dispatch
      47                 :   // __atomic_add_dispatch
      48                 : #ifdef _GLIBCXX_ATOMIC_BUILTINS
      49                 :   static inline _Atomic_word 
      50               0 :   __exchange_and_add(volatile _Atomic_word* __mem, int __val)
      51               0 :   { return __sync_fetch_and_add(__mem, __val); }
      52                 : 
      53                 :   static inline void
      54                 :   __atomic_add(volatile _Atomic_word* __mem, int __val)
      55                 :   { __sync_fetch_and_add(__mem, __val); }
      56                 : #else
      57                 :   _Atomic_word
      58                 :   __attribute__ ((__unused__))
      59                 :   __exchange_and_add(volatile _Atomic_word*, int);
      60                 : 
      61                 :   void
      62                 :   __attribute__ ((__unused__))
      63                 :   __atomic_add(volatile _Atomic_word*, int);
      64                 : #endif
      65                 : 
      66                 :   static inline _Atomic_word
      67               0 :   __exchange_and_add_single(_Atomic_word* __mem, int __val)
      68                 :   {
      69               0 :     _Atomic_word __result = *__mem;
      70               0 :     *__mem += __val;
      71               0 :     return __result;
      72                 :   }
      73                 : 
      74                 :   static inline void
      75                 :   __atomic_add_single(_Atomic_word* __mem, int __val)
      76                 :   { *__mem += __val; }
      77                 : 
      78                 :   static inline _Atomic_word
      79                 :   __attribute__ ((__unused__))
      80               0 :   __exchange_and_add_dispatch(_Atomic_word* __mem, int __val)
      81                 :   {
      82                 : #ifdef __GTHREADS
      83               0 :     if (__gthread_active_p())
      84               0 :       return __exchange_and_add(__mem, __val);
      85                 :     else
      86               0 :       return __exchange_and_add_single(__mem, __val);
      87                 : #else
      88                 :     return __exchange_and_add_single(__mem, __val);
      89                 : #endif
      90                 :   }
      91                 : 
      92                 :   static inline void
      93                 :   __attribute__ ((__unused__))
      94                 :   __atomic_add_dispatch(_Atomic_word* __mem, int __val)
      95                 :   {
      96                 : #ifdef __GTHREADS
      97                 :     if (__gthread_active_p())
      98                 :       __atomic_add(__mem, __val);
      99                 :     else
     100                 :       __atomic_add_single(__mem, __val);
     101                 : #else
     102                 :     __atomic_add_single(__mem, __val);
     103                 : #endif
     104                 :   }
     105                 : 
     106                 : _GLIBCXX_END_NAMESPACE
     107                 : 
     108                 : // Even if the CPU doesn't need a memory barrier, we need to ensure
     109                 : // that the compiler doesn't reorder memory accesses across the
     110                 : // barriers.
     111                 : #ifndef _GLIBCXX_READ_MEM_BARRIER
     112                 : #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory")
     113                 : #endif
     114                 : #ifndef _GLIBCXX_WRITE_MEM_BARRIER
     115                 : #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory")
     116                 : #endif
     117                 : 
     118                 : #endif