1  // Low-level functions for atomic operations: Generic version  -*- C++ -*-
       2  
       3  // Copyright (C) 1999-2023 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 3, 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  // Under Section 7 of GPL version 3, you are granted additional
      17  // permissions described in the GCC Runtime Library Exception, version
      18  // 3.1, as published by the Free Software Foundation.
      19  
      20  // You should have received a copy of the GNU General Public License and
      21  // a copy of the GCC Runtime Library Exception along with this program;
      22  // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23  // <http://www.gnu.org/licenses/>.
      24  
      25  #include <ext/atomicity.h>
      26  #include <ext/concurrence.h>
      27  
      28  namespace
      29  {
      30    __gnu_cxx::__mutex&
      31    get_atomic_mutex()
      32    {
      33      static __gnu_cxx::__mutex atomic_mutex;
      34      return atomic_mutex;
      35    }
      36  } // anonymous namespace
      37  
      38  namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
      39  {
      40  _GLIBCXX_BEGIN_NAMESPACE_VERSION
      41  
      42    _Atomic_word
      43    __attribute__ ((__unused__))
      44    __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw ()
      45    {
      46      __gnu_cxx::__scoped_lock sentry(get_atomic_mutex());
      47      _Atomic_word __result;
      48      __result = *__mem;
      49      *__mem += __val;
      50      return __result;
      51    }
      52  
      53    void
      54    __attribute__ ((__unused__))
      55    __atomic_add(volatile _Atomic_word* __mem, int __val) throw ()
      56    { __exchange_and_add(__mem, __val); }
      57  
      58  _GLIBCXX_END_NAMESPACE_VERSION
      59  } // namespace