1                 : // Support for atomic operations -*- C++ -*-
       2                 : 
       3                 : // Copyright (C) 2004, 2005, 2006, 2008, 2009, 2010
       4                 : // Free Software Foundation, Inc.
       5                 : //
       6                 : // This file is part of the GNU ISO C++ Library.  This library is free
       7                 : // software; you can redistribute it and/or modify it under the
       8                 : // terms of the GNU General Public License as published by the
       9                 : // Free Software Foundation; either version 3, or (at your option)
      10                 : // any later version.
      11                 : 
      12                 : // This library is distributed in the hope that it will be useful,
      13                 : // but WITHOUT ANY WARRANTY; without even the implied warranty of
      14                 : // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      15                 : // GNU General Public License for more details.
      16                 : 
      17                 : // Under Section 7 of GPL version 3, you are granted additional
      18                 : // permissions described in the GCC Runtime Library Exception, version
      19                 : // 3.1, as published by the Free Software Foundation.
      20                 : 
      21                 : // You should have received a copy of the GNU General Public License and
      22                 : // a copy of the GCC Runtime Library Exception along with this program;
      23                 : // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      24                 : // <http://www.gnu.org/licenses/>.
      25                 : 
      26                 : /** @file ext/atomicity.h
      27                 :  *  This file is a GNU extension to the Standard C++ Library.
      28                 :  */
      29                 : 
      30                 : #ifndef _GLIBCXX_ATOMICITY_H
      31                 : #define _GLIBCXX_ATOMICITY_H    1
      32                 : 
      33                 : #include <bits/c++config.h>
      34                 : #include <bits/gthr.h>
      35                 : #include <bits/atomic_word.h>
      36                 : 
      37                 : namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
      38                 : {
      39                 : _GLIBCXX_BEGIN_NAMESPACE_VERSION
      40                 : 
      41                 :   // Functions for portable atomic access.
      42                 :   // To abstract locking primitives across all thread policies, use:
      43                 :   // __exchange_and_add_dispatch
      44                 :   // __atomic_add_dispatch
      45                 : #ifdef _GLIBCXX_ATOMIC_BUILTINS_4
      46                 :   static inline _Atomic_word 
      47               0 :   __exchange_and_add(volatile _Atomic_word* __mem, int __val)
      48               0 :   { return __sync_fetch_and_add(__mem, __val); }
      49                 : 
      50                 :   static inline void
      51                 :   __atomic_add(volatile _Atomic_word* __mem, int __val)
      52                 :   { __sync_fetch_and_add(__mem, __val); }
      53                 : #else
      54                 :   _Atomic_word
      55                 :   __attribute__ ((__unused__))
      56                 :   __exchange_and_add(volatile _Atomic_word*, int) throw ();
      57                 : 
      58                 :   void
      59                 :   __attribute__ ((__unused__))
      60                 :   __atomic_add(volatile _Atomic_word*, int) throw ();
      61                 : #endif
      62                 : 
      63                 :   static inline _Atomic_word
      64               0 :   __exchange_and_add_single(_Atomic_word* __mem, int __val)
      65                 :   {
      66               0 :     _Atomic_word __result = *__mem;
      67               0 :     *__mem += __val;
      68               0 :     return __result;
      69                 :   }
      70                 : 
      71                 :   static inline void
      72                 :   __atomic_add_single(_Atomic_word* __mem, int __val)
      73                 :   { *__mem += __val; }
      74                 : 
      75                 :   static inline _Atomic_word
      76                 :   __attribute__ ((__unused__))
      77               0 :   __exchange_and_add_dispatch(_Atomic_word* __mem, int __val)
      78                 :   {
      79                 : #ifdef __GTHREADS
      80               0 :     if (__gthread_active_p())
      81               0 :       return __exchange_and_add(__mem, __val);
      82                 :     else
      83               0 :       return __exchange_and_add_single(__mem, __val);
      84                 : #else
      85                 :     return __exchange_and_add_single(__mem, __val);
      86                 : #endif
      87                 :   }
      88                 : 
      89                 :   static inline void
      90                 :   __attribute__ ((__unused__))
      91                 :   __atomic_add_dispatch(_Atomic_word* __mem, int __val)
      92                 :   {
      93                 : #ifdef __GTHREADS
      94                 :     if (__gthread_active_p())
      95                 :       __atomic_add(__mem, __val);
      96                 :     else
      97                 :       __atomic_add_single(__mem, __val);
      98                 : #else
      99                 :     __atomic_add_single(__mem, __val);
     100                 : #endif
     101                 :   }
     102                 : 
     103                 : _GLIBCXX_END_NAMESPACE_VERSION
     104                 : } // namespace
     105                 : 
     106                 : // Even if the CPU doesn't need a memory barrier, we need to ensure
     107                 : // that the compiler doesn't reorder memory accesses across the
     108                 : // barriers.
     109                 : #ifndef _GLIBCXX_READ_MEM_BARRIER
     110                 : #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory")
     111                 : #endif
     112                 : #ifndef _GLIBCXX_WRITE_MEM_BARRIER
     113                 : #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory")
     114                 : #endif
     115                 : 
     116                 : #endif