Line data    Source code

       1             : // Support for atomic operations -*- C++ -*-
       2             : 
       3             : // Copyright (C) 2004-2021 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             : /** @file ext/atomicity.h
      26             :  *  This file is a GNU extension to the Standard C++ Library.
      27             :  */
      28             : 
      29             : #ifndef _GLIBCXX_ATOMICITY_H
      30             : #define _GLIBCXX_ATOMICITY_H    1
      31             : 
      32             : #pragma GCC system_header
      33             : 
      34             : #include <bits/c++config.h>
      35             : #include <bits/gthr.h>
      36             : #include <bits/atomic_word.h>
      37             : #if __has_include(<sys/single_threaded.h>)
      38             : # include <sys/single_threaded.h>
      39             : #endif
      40             : 
      41             : namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
      42             : {
      43             : _GLIBCXX_BEGIN_NAMESPACE_VERSION
      44             : 
      45             :   __attribute__((__always_inline__))
      46             :   inline bool
      47             :   __is_single_threaded() _GLIBCXX_NOTHROW
      48             :   {
      49             : #ifndef __GTHREADS
      50             :     return true;
      51             : #elif __has_include(<sys/single_threaded.h>)
      52    50209135 :     return ::__libc_single_threaded;
      53             : #else
      54             :     return !__gthread_active_p();
      55             : #endif
      56             :   }
      57             : 
      58             :   // Functions for portable atomic access.
      59             :   // To abstract locking primitives across all thread policies, use:
      60             :   // __exchange_and_add_dispatch
      61             :   // __atomic_add_dispatch
      62             : #ifdef _GLIBCXX_ATOMIC_BUILTINS
      63             :   inline _Atomic_word
      64             :   __attribute__((__always_inline__))
      65             :   __exchange_and_add(volatile _Atomic_word* __mem, int __val)
      66    35571579 :   { return __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); }
      67             : 
      68             :   inline void
      69             :   __attribute__((__always_inline__))
      70             :   __atomic_add(volatile _Atomic_word* __mem, int __val)
      71    14630458 :   { __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); }
      72             : #else
      73             :   _Atomic_word
      74             :   __exchange_and_add(volatile _Atomic_word*, int) _GLIBCXX_NOTHROW;
      75             : 
      76             :   void
      77             :   __atomic_add(volatile _Atomic_word*, int) _GLIBCXX_NOTHROW;
      78             : #endif
      79             : 
      80             :   inline _Atomic_word
      81             :   __attribute__((__always_inline__))
      82             :   __exchange_and_add_single(_Atomic_word* __mem, int __val)
      83             :   {
      84        3527 :     _Atomic_word __result = *__mem;
      85        3527 :     *__mem += __val;
      86        3527 :     return __result;
      87             :   }
      88             : 
      89             :   inline void
      90             :   __attribute__((__always_inline__))
      91             :   __atomic_add_single(_Atomic_word* __mem, int __val)
      92        3571 :   { *__mem += __val; }
      93             : 
      94             :   inline _Atomic_word
      95             :   __attribute__ ((__always_inline__))
      96             :   __exchange_and_add_dispatch(_Atomic_word* __mem, int __val)
      97             :   {
      98    35575106 :     if (__is_single_threaded())
      99        3527 :       return __exchange_and_add_single(__mem, __val);
     100             :     else
     101    35571579 :       return __exchange_and_add(__mem, __val);
     102             :   }
     103             : 
     104             :   inline void
     105             :   __attribute__ ((__always_inline__))
     106             :   __atomic_add_dispatch(_Atomic_word* __mem, int __val)
     107             :   {
     108    14634029 :     if (__is_single_threaded())
     109             :       __atomic_add_single(__mem, __val);
     110             :     else
     111             :       __atomic_add(__mem, __val);
     112    14634029 :   }
     113             : 
     114             : _GLIBCXX_END_NAMESPACE_VERSION
     115             : } // namespace
     116             : 
     117             : // Even if the CPU doesn't need a memory barrier, we need to ensure
     118             : // that the compiler doesn't reorder memory accesses across the
     119             : // barriers.
     120             : #ifndef _GLIBCXX_READ_MEM_BARRIER
     121             : #define _GLIBCXX_READ_MEM_BARRIER __atomic_thread_fence (__ATOMIC_ACQUIRE)
     122             : #endif
     123             : #ifndef _GLIBCXX_WRITE_MEM_BARRIER
     124             : #define _GLIBCXX_WRITE_MEM_BARRIER __atomic_thread_fence (__ATOMIC_RELEASE)
     125             : #endif
     126             : 
     127             : #endif