mutex.cc revision 1.5 
1// mutex -*- C++ -*-
2
3// Copyright (C) 2008-2017 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 <mutex>
26
27#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
28#ifndef _GLIBCXX_HAVE_TLS
29namespace
30{
31  inline std::unique_lock<std::mutex>*&
32  __get_once_functor_lock_ptr()
33  {
34    static std::unique_lock<std::mutex>* __once_functor_lock_ptr = 0;
35    return __once_functor_lock_ptr;
36  }
37}
38#endif
39
40namespace std _GLIBCXX_VISIBILITY(default)
41{
42_GLIBCXX_BEGIN_NAMESPACE_VERSION
43
44#ifdef _GLIBCXX_HAVE_TLS
45  __thread void* __once_callable;
46  __thread void (*__once_call)();
47#else
48  // Explicit instantiation due to -fno-implicit-instantiation.
49  template class function<void()>;
50  function<void()> __once_functor;
51
52  mutex&
53  __get_once_mutex()
54  {
55    static mutex once_mutex;
56    return once_mutex;
57  }
58
59  // code linked against ABI 3.4.12 and later uses this
60  void
61  __set_once_functor_lock_ptr(unique_lock<mutex>* __ptr)
62  {
63    __get_once_functor_lock_ptr() = __ptr;
64  }
65
66  // unsafe - retained for compatibility with ABI 3.4.11
67  unique_lock<mutex>&
68  __get_once_functor_lock()
69  {
70    static unique_lock<mutex> once_functor_lock(__get_once_mutex(), defer_lock);
71    return once_functor_lock;
72  }
73#endif
74
75  extern "C"
76  {
77    void __once_proxy()
78    {
79#ifndef _GLIBCXX_HAVE_TLS
80      function<void()> __once_call = std::move(__once_functor);
81      if (unique_lock<mutex>* __lock = __get_once_functor_lock_ptr())
82      {
83        // caller is using new ABI and provided lock ptr
84        __get_once_functor_lock_ptr() = 0;
85        __lock->unlock();
86      }
87      else
88        __get_once_functor_lock().unlock();  // global lock
89#endif
90      __once_call();
91    }
92  }
93
94_GLIBCXX_END_NAMESPACE_VERSION
95} // namespace std
96
97#endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
98