# atomicity.h

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    00001 // Support for atomic operations -*- C++ -*-
    00002
    00003 // Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
    00004 //
    00005 // This file is part of the GNU ISO C++ Library.  This library is free
    00006 // software; you can redistribute it and/or modify it under the
    00007 // terms of the GNU General Public License as published by the
    00008 // Free Software Foundation; either version 2, or (at your option)
    00009 // any later version.
    00010
    00011 // This library is distributed in the hope that it will be useful,
    00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
    00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00014 // GNU General Public License for more details.
    00015
    00016 // You should have received a copy of the GNU General Public License along
    00017 // with this library; see the file COPYING.  If not, write to the Free
    00018 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
    00019 // USA.
    00020
    00021 // As a special exception, you may use this file as part of a free software
    00022 // library without restriction.  Specifically, if other files instantiate
    00023 // templates or use macros or inline functions from this file, or you compile
    00024 // this file and link it with other files to produce an executable, this
    00025 // file does not by itself cause the resulting executable to be covered by
    00026 // the GNU General Public License.  This exception does not however
    00027 // invalidate any other reasons why the executable file might be covered by
    00028 // the GNU General Public License.
    00029
    00030 /** @file atomicity.h
    00031  *  This is an internal header file, included by other library headers.
    00032  *  You should not attempt to use it directly.
    00033  */
    00034
    00035 #ifndef _GLIBCXX_ATOMICITY_H
    00036 #define _GLIBCXX_ATOMICITY_H    1
    00037
    00038 #include <bits/c++config.h>
    00039 #include <bits/gthr.h>
    00040 #include <bits/atomic_word.h>
    00041
    00042 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
    00043
    00044   // Functions for portable atomic access.
    00045   // To abstract locking primitives across all thread policies, use:
    00046   // __exchange_and_add_dispatch
    00047   // __atomic_add_dispatch
    00048 #ifdef _GLIBCXX_ATOMIC_BUILTINS
    00049   static inline _Atomic_word
    00050   __exchange_and_add(volatile _Atomic_word* __mem, int __val)
    00051   { return __sync_fetch_and_add(__mem, __val); }
    00052
    00053   static inline void
    00054   __atomic_add(volatile _Atomic_word* __mem, int __val)
    00055   { __sync_fetch_and_add(__mem, __val); }
    00056 #else
    00057   _Atomic_word
    00058   __attribute__ ((__unused__))
    00059   __exchange_and_add(volatile _Atomic_word*, int);
    00060
    00061   void
    00062   __attribute__ ((__unused__))
    00063   __atomic_add(volatile _Atomic_word*, int);
    00064 #endif
    00065
    00066   static inline _Atomic_word
    00067   __exchange_and_add_single(_Atomic_word* __mem, int __val)
    00068   {
    00069     _Atomic_word __result = *__mem;
    00070     *__mem += __val;
    00071     return __result;
    00072   }
    00073
    00074   static inline void
    00075   __atomic_add_single(_Atomic_word* __mem, int __val)
    00076   { *__mem += __val; }
    00077
    00078   static inline _Atomic_word
    00079   __attribute__ ((__unused__))
    00080   __exchange_and_add_dispatch(_Atomic_word* __mem, int __val)
    00081   {
    00082 #ifdef __GTHREADS
    00083     if (__gthread_active_p())
    00084       return __exchange_and_add(__mem, __val);
    00085     else
    00086       return __exchange_and_add_single(__mem, __val);
    00087 #else
    00088     return __exchange_and_add_single(__mem, __val);
    00089 #endif
    00090   }
    00091
    00092   static inline void
    00093   __attribute__ ((__unused__))
    00094   __atomic_add_dispatch(_Atomic_word* __mem, int __val)
    00095   {
    00096 #ifdef __GTHREADS
    00097     if (__gthread_active_p())
    00098       __atomic_add(__mem, __val);
    00099     else
    00100       __atomic_add_single(__mem, __val);
    00101 #else
    00102     __atomic_add_single(__mem, __val);
    00103 #endif
    00104   }
    00105
    00106 _GLIBCXX_END_NAMESPACE
    00107
    00108 // Even if the CPU doesn't need a memory barrier, we need to ensure
    00109 // that the compiler doesn't reorder memory accesses across the
    00110 // barriers.
    00111 #ifndef _GLIBCXX_READ_MEM_BARRIER
    00112 #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory")
    00113 #endif
    00114 #ifndef _GLIBCXX_WRITE_MEM_BARRIER
    00115 #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory")
    00116 #endif
    00117
    00118 #endif