237 lines
8.0 KiB
C++
237 lines
8.0 KiB
C++
// Threading support -*- C++ -*-
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// Copyright (C) 2001 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 2, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License along
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// with this library; see the file COPYING. If not, write to the Free
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// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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// USA.
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// As a special exception, you may use this file as part of a free software
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// library without restriction. Specifically, if other files instantiate
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// templates or use macros or inline functions from this file, or you compile
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// this file and link it with other files to produce an executable, this
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// file does not by itself cause the resulting executable to be covered by
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// the GNU General Public License. This exception does not however
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// invalidate any other reasons why the executable file might be covered by
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// the GNU General Public License.
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/*
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* Copyright (c) 1997-1999
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* Silicon Graphics Computer Systems, Inc.
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*
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* Permission to use, copy, modify, distribute and sell this software
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* and its documentation for any purpose is hereby granted without fee,
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* provided that the above copyright notice appear in all copies and
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* that both that copyright notice and this permission notice appear
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* in supporting documentation. Silicon Graphics makes no
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* representations about the suitability of this software for any
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* purpose. It is provided "as is" without express or implied warranty.
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*/
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/** @file stl_threads.h
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* This is an internal header file, included by other library headers.
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* You should not attempt to use it directly.
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*/
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#ifndef __SGI_STL_INTERNAL_THREADS_H
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#define __SGI_STL_INTERNAL_THREADS_H
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// The only supported threading model is GCC's own gthr.h abstraction layer.
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#include "bits/gthr.h"
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namespace std
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{
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// Class _Refcount_Base provides a type, _RC_t, a data member,
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// _M_ref_count, and member functions _M_incr and _M_decr, which perform
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// atomic preincrement/predecrement. The constructor initializes
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// _M_ref_count.
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struct _Refcount_Base
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{
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// The type _RC_t
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typedef size_t _RC_t;
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// The data member _M_ref_count
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volatile _RC_t _M_ref_count;
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// Constructor
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__gthread_mutex_t _M_ref_count_lock;
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_Refcount_Base(_RC_t __n) : _M_ref_count(__n)
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{
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#ifdef __GTHREAD_MUTEX_INIT
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__gthread_mutex_t __tmp = __GTHREAD_MUTEX_INIT;
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_M_ref_count_lock = __tmp;
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#elif defined(__GTHREAD_MUTEX_INIT_FUNCTION)
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__GTHREAD_MUTEX_INIT_FUNCTION (&_M_ref_count_lock);
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#else
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#error __GTHREAD_MUTEX_INIT or __GTHREAD_MUTEX_INIT_FUNCTION should be defined by gthr.h abstraction layer, report problem to libstdc++@gcc.gnu.org.
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#endif
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}
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void
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_M_incr()
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{
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__gthread_mutex_lock(&_M_ref_count_lock);
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++_M_ref_count;
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__gthread_mutex_unlock(&_M_ref_count_lock);
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}
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_RC_t
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_M_decr()
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{
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__gthread_mutex_lock(&_M_ref_count_lock);
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volatile _RC_t __tmp = --_M_ref_count;
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__gthread_mutex_unlock(&_M_ref_count_lock);
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return __tmp;
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}
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};
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// Atomic swap on unsigned long
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// This is guaranteed to behave as though it were atomic only if all
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// possibly concurrent updates use _Atomic_swap.
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// In some cases the operation is emulated with a lock.
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#if defined (__GTHREAD_MUTEX_INIT)
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// This could be optimized to use the atomicity.h abstraction layer.
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// vyzo: simple _Atomic_swap implementation following the guidelines above
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// We use a template here only to get a unique initialized instance.
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template<int __dummy>
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struct _Swap_lock_struct
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{ static __gthread_mutex_t _S_swap_lock; };
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template<int __dummy>
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__gthread_mutex_t
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_Swap_lock_struct<__dummy>::_S_swap_lock = __GTHREAD_MUTEX_INIT;
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// This should be portable, but performance is expected to be quite
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// awful. This really needs platform specific code.
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inline unsigned long
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_Atomic_swap(unsigned long * __p, unsigned long __q)
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{
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__gthread_mutex_lock(&_Swap_lock_struct<0>::_S_swap_lock);
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unsigned long __result = *__p;
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*__p = __q;
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__gthread_mutex_unlock(&_Swap_lock_struct<0>::_S_swap_lock);
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return __result;
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}
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#endif
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// Locking class. Note that this class *does not have a
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// constructor*. It must be initialized either statically, with
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// __STL_MUTEX_INITIALIZER, or dynamically, by explicitly calling
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// the _M_initialize member function. (This is similar to the ways
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// that a pthreads mutex can be initialized.) There are explicit
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// member functions for acquiring and releasing the lock.
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// There is no constructor because static initialization is
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// essential for some uses, and only a class aggregate (see section
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// 8.5.1 of the C++ standard) can be initialized that way. That
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// means we must have no constructors, no base classes, no virtual
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// functions, and no private or protected members.
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#if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
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extern __gthread_mutex_t _GLIBCPP_mutex;
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extern __gthread_mutex_t *_GLIBCPP_mutex_address;
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extern __gthread_once_t _GLIBCPP_once;
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extern void _GLIBCPP_mutex_init (void);
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extern void _GLIBCPP_mutex_address_init (void);
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#endif
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struct _STL_mutex_lock
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{
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// The class must be statically initialized with __STL_MUTEX_INITIALIZER.
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#if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
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volatile int _M_init_flag;
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__gthread_once_t _M_once;
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#endif
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__gthread_mutex_t _M_lock;
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void
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_M_initialize()
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{
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#ifdef __GTHREAD_MUTEX_INIT
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// There should be no code in this path given the usage rules above.
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#elif defined(__GTHREAD_MUTEX_INIT_FUNCTION)
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if (_M_init_flag) return;
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if (__gthread_once (&_GLIBCPP_once, _GLIBCPP_mutex_init) != 0
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&& __gthread_active_p ())
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abort ();
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__gthread_mutex_lock (&_GLIBCPP_mutex);
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if (!_M_init_flag)
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{
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// Even though we have a global lock, we use __gthread_once to be
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// absolutely certain the _M_lock mutex is only initialized once on
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// multiprocessor systems.
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_GLIBCPP_mutex_address = &_M_lock;
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if (__gthread_once (&_M_once, _GLIBCPP_mutex_address_init) != 0
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&& __gthread_active_p ())
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abort ();
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_M_init_flag = 1;
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}
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__gthread_mutex_unlock (&_GLIBCPP_mutex);
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#endif
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}
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void
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_M_acquire_lock()
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{
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#if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
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if (!_M_init_flag) _M_initialize();
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#endif
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__gthread_mutex_lock(&_M_lock);
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}
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void
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_M_release_lock()
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{
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#if !defined(__GTHREAD_MUTEX_INIT) && defined(__GTHREAD_MUTEX_INIT_FUNCTION)
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if (!_M_init_flag) _M_initialize();
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#endif
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__gthread_mutex_unlock(&_M_lock);
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}
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};
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#ifdef __GTHREAD_MUTEX_INIT
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#define __STL_MUTEX_INITIALIZER = { __GTHREAD_MUTEX_INIT }
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#elif defined(__GTHREAD_MUTEX_INIT_FUNCTION)
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#ifdef __GTHREAD_MUTEX_INIT_DEFAULT
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#define __STL_MUTEX_INITIALIZER \
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= { 0, __GTHREAD_ONCE_INIT, __GTHREAD_MUTEX_INIT_DEFAULT }
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#else
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#define __STL_MUTEX_INITIALIZER = { 0, __GTHREAD_ONCE_INIT }
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#endif
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#endif
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// A locking class that uses _STL_mutex_lock. The constructor takes a
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// reference to an _STL_mutex_lock, and acquires a lock. The
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// destructor releases the lock. It's not clear that this is exactly
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// the right functionality. It will probably change in the future.
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struct _STL_auto_lock
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{
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_STL_mutex_lock& _M_lock;
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_STL_auto_lock(_STL_mutex_lock& __lock) : _M_lock(__lock)
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{ _M_lock._M_acquire_lock(); }
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~_STL_auto_lock() { _M_lock._M_release_lock(); }
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private:
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void operator=(const _STL_auto_lock&);
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_STL_auto_lock(const _STL_auto_lock&);
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};
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} // namespace std
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#endif
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