libstdc++-v3/src/atomic.cc

   1 // Support for atomic operations -*- C++ -*-
   2
   3 // Copyright (C) 2008, 2009
   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 #include "gstdint.h"
  27 #include <cstdatomic>
  28 #include <mutex>
  29
  30 #define LOGSIZE 4
  31
  32 namespace
  33 {
  34 #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
  35   std::mutex&
  36   get_atomic_mutex()
  37   {
  38     static std::mutex atomic_mutex;
  39     return atomic_mutex;
  40   }
  41 #endif
  42
  43   std::__atomic_flag_base volatile flag_table[ 1 << LOGSIZE ] =
  44     {
  45       ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT,
  46       ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT,
  47       ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT,
  48       ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT, ATOMIC_FLAG_INIT,
  49     };
  50 } // anonymous namespace
  51
  52 namespace std
  53 {
  54   namespace __atomic0
  55   {
  56     bool
  57     atomic_flag::test_and_set(memory_order) volatile
  58     {
  59 #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
  60       lock_guard<mutex> __lock(get_atomic_mutex());
  61 #endif
  62       bool result = _M_i;
  63       _M_i = true;
  64       return result;
  65     }
  66
  67     void
  68     atomic_flag::clear(memory_order) volatile
  69     {
  70 #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
  71       lock_guard<mutex> __lock(get_atomic_mutex());
  72 #endif
  73       _M_i = false;
  74     }
  75   }
  76
  77   extern "C"
  78   {
  79     bool
  80     atomic_flag_test_and_set_explicit(volatile __atomic_flag_base* __a,
  81                                       memory_order __m) throw ()
  82     {
  83       volatile atomic_flag* d = static_cast<volatile atomic_flag*>(__a);
  84       return d->test_and_set(__m);
  85     }
  86
  87     void
  88     atomic_flag_clear_explicit(volatile __atomic_flag_base* __a,
  89                                memory_order __m) throw ()
  90     {
  91       volatile atomic_flag* d = static_cast<volatile atomic_flag*>(__a);
  92       return d->clear(__m);
  93     }
  94
  95     void
  96     __atomic_flag_wait_explicit(volatile __atomic_flag_base* __a,
  97                                 memory_order __x) throw ()
  98     {
  99       while (atomic_flag_test_and_set_explicit(__a, __x))
 100         { };
 101     }
 102
 103     volatile __atomic_flag_base*
 104     __atomic_flag_for_address(const volatile void* __z) throw ()
 105     {
 106       uintptr_t __u = reinterpret_cast<uintptr_t>(__z);
 107       __u += (__u >> 2) + (__u << 4);
 108       __u += (__u >> 7) + (__u << 5);
 109       __u += (__u >> 17) + (__u << 13);
 110       if (sizeof(uintptr_t) > 4)
 111         __u += (__u >> 31);
 112       __u &= ~((~uintptr_t(0)) << LOGSIZE);
 113       return flag_table + __u;
 114     }
 115   } // extern "C"
 116 } // namespace std