libstdc++-v3/include/bits/stl_threads.h

   1 // Threading support -*- C++ -*-
   2
   3 // Copyright (C) 2001, 2002, 2003 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 2, 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 // You should have received a copy of the GNU General Public License along
  17 // with this library; see the file COPYING.  If not, write to the Free
  18 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  19 // USA.
  20
  21 // As a special exception, you may use this file as part of a free software
  22 // library without restriction.  Specifically, if other files instantiate
  23 // templates or use macros or inline functions from this file, or you compile
  24 // this file and link it with other files to produce an executable, this
  25 // file does not by itself cause the resulting executable to be covered by
  26 // the GNU General Public License.  This exception does not however
  27 // invalidate any other reasons why the executable file might be covered by
  28 // the GNU General Public License.
  29
  30 /*
  31  * Copyright (c) 1997-1999
  32  * Silicon Graphics Computer Systems, Inc.
  33  *
  34  * Permission to use, copy, modify, distribute and sell this software
  35  * and its documentation for any purpose is hereby granted without fee,
  36  * provided that the above copyright notice appear in all copies and
  37  * that both that copyright notice and this permission notice appear
  38  * in supporting documentation.  Silicon Graphics makes no
  39  * representations about the suitability of this software for any
  40  * purpose.  It is provided "as is" without express or implied warranty.
  41  */
  42
  43 /** @file stl_threads.h
  44  *  This is an internal header file, included by other library headers.
  45  *  You should not attempt to use it directly.
  46  */
  47
  48 #ifndef _STL_THREADS_H
  49 #define _STL_THREADS_H 1
  50
  51 #include <cstddef>
  52
  53 // The only supported threading model is GCC's own gthr.h abstraction
  54 // layer.
  55 #include "bits/gthr.h"
  56
  57 namespace __gnu_cxx
  58 {
  59 #if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
  60   extern __gthread_mutex_t _GLIBCXX_mutex;
  61   extern __gthread_mutex_t *_GLIBCXX_mutex_address;
  62   extern __gthread_once_t _GLIBCXX_once;
  63   extern void _GLIBCXX_mutex_init(void);
  64   extern void _GLIBCXX_mutex_address_init(void);
  65 #endif
  66
  67   // Locking class.  Note that this class *does not have a
  68   // constructor*.  It must be initialized either statically, with
  69   // __STL_MUTEX_INITIALIZER, or dynamically, by explicitly calling
  70   // the _M_initialize member function.  (This is similar to the ways
  71   // that a pthreads mutex can be initialized.)  There are explicit
  72   // member functions for acquiring and releasing the lock.
  73
  74   // There is no constructor because static initialization is
  75   // essential for some uses, and only a class aggregate (see section
  76   // 8.5.1 of the C++ standard) can be initialized that way.  That
  77   // means we must have no constructors, no base classes, no virtual
  78   // functions, and no private or protected members.
  79   struct _STL_mutex_lock
  80   {
  81     // The class must be statically initialized with __STL_MUTEX_INITIALIZER.
  82 #if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
  83     volatile int _M_init_flag;
  84     __gthread_once_t _M_once;
  85 #endif
  86     __gthread_mutex_t _M_lock;
  87
  88     void
  89     _M_initialize()
  90     {
  91 #ifdef __GTHREAD_MUTEX_INIT
  92       // There should be no code in this path given the usage rules above.
  93 #elif defined(__GTHREAD_MUTEX_INIT_FUNCTION)
  94       if (_M_init_flag) return;
  95       if (__gthread_once(&__gnu_cxx::_GLIBCXX_once,
  96                          __gnu_cxx::_GLIBCXX_mutex_init) != 0
  97           && __gthread_active_p())
  98         abort ();
  99       __gthread_mutex_lock(&__gnu_cxx::_GLIBCXX_mutex);
 100       if (!_M_init_flag)
 101         {
 102           // Even though we have a global lock, we use __gthread_once to be
 103           // absolutely certain the _M_lock mutex is only initialized once on
 104           // multiprocessor systems.
 105           __gnu_cxx::_GLIBCXX_mutex_address = &_M_lock;
 106           if (__gthread_once(&_M_once,
 107                              __gnu_cxx::_GLIBCXX_mutex_address_init) != 0
 108             && __gthread_active_p())
 109             abort();
 110           _M_init_flag = 1;
 111         }
 112       __gthread_mutex_unlock(&__gnu_cxx::_GLIBCXX_mutex);
 113 #endif
 114     }
 115
 116     void
 117     _M_acquire_lock()
 118     {
 119 #if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
 120       if (!_M_init_flag) _M_initialize();
 121 #endif
 122       __gthread_mutex_lock(&_M_lock);
 123     }
 124
 125     void
 126     _M_release_lock()
 127     {
 128 #if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
 129       if (!_M_init_flag) _M_initialize();
 130 #endif
 131       __gthread_mutex_unlock(&_M_lock);
 132     }
 133   };
 134
 135 #ifdef __GTHREAD_MUTEX_INIT
 136 #define __STL_MUTEX_INITIALIZER = { __GTHREAD_MUTEX_INIT }
 137 #elif defined(__GTHREAD_MUTEX_INIT_FUNCTION)
 138 #ifdef __GTHREAD_MUTEX_INIT_DEFAULT
 139 #define __STL_MUTEX_INITIALIZER \
 140   = { 0, __GTHREAD_ONCE_INIT, __GTHREAD_MUTEX_INIT_DEFAULT }
 141 #else
 142 #define __STL_MUTEX_INITIALIZER = { 0, __GTHREAD_ONCE_INIT }
 143 #endif
 144 #endif
 145 } // namespace __gnu_cxx
 146
 147 #endif