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