Home | History | Annotate | Line # | Download | only in i386 
      1 // Low-level functions for atomic operations: x86, x >= 3 version  -*- C++ -*-
      2 
      3 // Copyright (C) 2003-2024 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 
     27 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
     28 {
     29 _GLIBCXX_BEGIN_NAMESPACE_VERSION
     30 
     31   template<int __inst>
     32     struct _Atomicity_lock
     33     {
     34       static volatile _Atomic_word _S_atomicity_lock;
     35     };
     36 
     37   template<int __inst>
     38   volatile _Atomic_word _Atomicity_lock<__inst>::_S_atomicity_lock = 0;
     39 
     40   template volatile _Atomic_word _Atomicity_lock<0>::_S_atomicity_lock;
     41 
     42   _Atomic_word
     43   __attribute__ ((__unused__))
     44   __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw ()
     45   {
     46     register _Atomic_word __result, __tmp = 1;
     47 
     48     // Obtain the atomic exchange/add spin lock.
     49     do
     50       {
     51 	__asm__ __volatile__ ("xchg{l} {%0,%1|%1,%0}"
     52 			      : "=m" (_Atomicity_lock<0>::_S_atomicity_lock),
     53 			      "+r" (__tmp)
     54 			      : "m" (_Atomicity_lock<0>::_S_atomicity_lock));
     55       }
     56     while (__tmp);
     57 
     58     __result = *__mem;
     59     *__mem += __val;
     60 
     61     // Release spin lock.
     62     _Atomicity_lock<0>::_S_atomicity_lock = 0;
     63 
     64     return __result;
     65   }
     66 
     67   void
     68   __attribute__ ((__unused__))
     69   __atomic_add(volatile _Atomic_word* __mem, int __val) throw ()
     70   { __exchange_and_add(__mem, __val); }
     71 
     72 _GLIBCXX_END_NAMESPACE_VERSION
     73 } // namespace
     74