# stl_threads.h

Go to the documentation of this file.

    00001 // Threading support -*- C++ -*-
    00002
    00003 // Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
    00004 //
    00005 // This file is part of the GNU ISO C++ Library.  This library is free
    00006 // software; you can redistribute it and/or modify it under the
    00007 // terms of the GNU General Public License as published by the
    00008 // Free Software Foundation; either version 2, or (at your option)
    00009 // any later version.
    00010
    00011 // This library is distributed in the hope that it will be useful,
    00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
    00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00014 // GNU General Public License for more details.
    00015
    00016 // You should have received a copy of the GNU General Public License along
    00017 // with this library; see the file COPYING.  If not, write to the Free
    00018 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
    00019 // USA.
    00020
    00021 // As a special exception, you may use this file as part of a free software
    00022 // library without restriction.  Specifically, if other files instantiate
    00023 // templates or use macros or inline functions from this file, or you compile
    00024 // this file and link it with other files to produce an executable, this
    00025 // file does not by itself cause the resulting executable to be covered by
    00026 // the GNU General Public License.  This exception does not however
    00027 // invalidate any other reasons why the executable file might be covered by
    00028 // the GNU General Public License.
    00029
    00030 /*
    00031  * Copyright (c) 1997-1999
    00032  * Silicon Graphics Computer Systems, Inc.
    00033  *
    00034  * Permission to use, copy, modify, distribute and sell this software
    00035  * and its documentation for any purpose is hereby granted without fee,
    00036  * provided that the above copyright notice appear in all copies and
    00037  * that both that copyright notice and this permission notice appear
    00038  * in supporting documentation.  Silicon Graphics makes no
    00039  * representations about the suitability of this software for any
    00040  * purpose.  It is provided "as is" without express or implied warranty.
    00041  */
    00042
    00043 /** @file stl_threads.h
    00044  *  This is an internal header file, included by other library headers.
    00045  *  You should not attempt to use it directly.
    00046  */
    00047
    00048 #ifndef _STL_THREADS_H
    00049 #define _STL_THREADS_H 1
    00050
    00051 #include <cstddef>
    00052
    00053 // The only supported threading model is GCC's own gthr.h abstraction
    00054 // layer.
    00055 #include "bits/gthr.h"
    00056
    00057 namespace __gnu_internal
    00058 {
    00059 #if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
    00060   extern __gthread_mutex_t _GLIBCXX_mutex;
    00061   extern __gthread_mutex_t *_GLIBCXX_mutex_address;
    00062   extern __gthread_once_t _GLIBCXX_once;
    00063   extern void _GLIBCXX_mutex_init(void);
    00064   extern void _GLIBCXX_mutex_address_init(void);
    00065 #endif
    00066 } // namespace __gnu_internal
    00067
    00068 namespace __gnu_cxx
    00069 {
    00070   // Locking class.  Note that this class *does not have a
    00071   // constructor*.  It must be initialized either statically, with
    00072   // __STL_MUTEX_INITIALIZER, or dynamically, by explicitly calling
    00073   // the _M_initialize member function.  (This is similar to the ways
    00074   // that a pthreads mutex can be initialized.)  There are explicit
    00075   // member functions for acquiring and releasing the lock.
    00076
    00077   // There is no constructor because static initialization is
    00078   // essential for some uses, and only a class aggregate (see section
    00079   // 8.5.1 of the C++ standard) can be initialized that way.  That
    00080   // means we must have no constructors, no base classes, no virtual
    00081   // functions, and no private or protected members.
    00082   struct _STL_mutex_lock
    00083   {
    00084     // The class must be statically initialized with __STL_MUTEX_INITIALIZER.
    00085 #if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
    00086     volatile int _M_init_flag;
    00087     __gthread_once_t _M_once;
    00088 #endif
    00089     __gthread_mutex_t _M_lock;
    00090
    00091     void
    00092     _M_initialize()
    00093     {
    00094 #ifdef __GTHREAD_MUTEX_INIT
    00095       // There should be no code in this path given the usage rules above.
    00096 #elif defined(__GTHREAD_MUTEX_INIT_FUNCTION)
    00097       if (_M_init_flag) return;
    00098       if (__gthread_once(&__gnu_internal::_GLIBCXX_once,
    00099              __gnu_internal::_GLIBCXX_mutex_init) != 0
    00100       && __gthread_active_p())
    00101     abort ();
    00102       __gthread_mutex_lock(&__gnu_internal::_GLIBCXX_mutex);
    00103       if (!_M_init_flag)
    00104     {
    00105       // Even though we have a global lock, we use __gthread_once to be
    00106       // absolutely certain the _M_lock mutex is only initialized once on
    00107       // multiprocessor systems.
    00108       __gnu_internal::_GLIBCXX_mutex_address = &_M_lock;
    00109       if (__gthread_once(&_M_once,
    00110                  __gnu_internal::_GLIBCXX_mutex_address_init) != 0
    00111         && __gthread_active_p())
    00112         abort();
    00113       _M_init_flag = 1;
    00114     }
    00115       __gthread_mutex_unlock(&__gnu_internal::_GLIBCXX_mutex);
    00116 #endif
    00117     }
    00118
    00119     void
    00120     _M_acquire_lock()
    00121     {
    00122 #if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
    00123       if (!_M_init_flag) _M_initialize();
    00124 #endif
    00125       __gthread_mutex_lock(&_M_lock);
    00126     }
    00127
    00128     void
    00129     _M_release_lock()
    00130     {
    00131 #if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
    00132       if (!_M_init_flag) _M_initialize();
    00133 #endif
    00134       __gthread_mutex_unlock(&_M_lock);
    00135     }
    00136   };
    00137
    00138 #ifdef __GTHREAD_MUTEX_INIT
    00139 #define __STL_MUTEX_INITIALIZER = { __GTHREAD_MUTEX_INIT }
    00140 #elif defined(__GTHREAD_MUTEX_INIT_FUNCTION)
    00141 #ifdef __GTHREAD_MUTEX_INIT_DEFAULT
    00142 #define __STL_MUTEX_INITIALIZER \
    00143   = { 0, __GTHREAD_ONCE_INIT, __GTHREAD_MUTEX_INIT_DEFAULT }
    00144 #else
    00145 #define __STL_MUTEX_INITIALIZER = { 0, __GTHREAD_ONCE_INIT }
    00146 #endif
    00147 #endif
    00148 } // namespace __gnu_cxx
    00149
    00150 #endif