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Whole document tree                   stl_threads.h Go to the documentation of this file. // 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. */ // WARNING: This is an internal header file, included by other C++ // standard library headers. You should not attempt to use this header // file directly. // Stl_config.h should be included before this file. #ifndef __SGI_STL_INTERNAL_THREADS_H #define __SGI_STL_INTERNAL_THREADS_H // Supported threading models are native SGI, pthreads, uithreads // (similar to pthreads, but based on an earlier draft of the Posix // threads standard), and Win32 threads. Uithread support by Jochen // Schlick, 1999. // GCC extension begin // In order to present a stable threading configuration, in all cases, // gcc looks for it's own abstraction layer before all others. All // modifications to this file are marked to allow easier importation of // STL upgrades. #if defined(__STL_GTHREADS) #include "bits/gthr.h" #else // GCC extension end #if defined(__STL_SGI_THREADS) #include <mutex.h> #include <time.h> #elif defined(__STL_PTHREADS) #include <pthread.h> #elif defined(__STL_UITHREADS) #include <thread.h> #include <synch.h> #elif defined(__STL_WIN32THREADS) #include <windows.h> #endif // GCC extension begin #endif // GCC extension end 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. // Hack for SGI o32 compilers. #if defined(__STL_SGI_THREADS) && !defined(__add_and_fetch) && \ (__mips < 3 || !(defined (_ABIN32) || defined(_ABI64))) # define __add_and_fetch(__l,__v) add_then_test((unsigned long*)__l,__v) # define __test_and_set(__l,__v) test_and_set(__l,__v) #endif /* o32 */ struct _Refcount_Base { // The type _RC_t # ifdef __STL_WIN32THREADS typedef long _RC_t; # else typedef size_t _RC_t; #endif // The data member _M_ref_count volatile _RC_t _M_ref_count; // Constructor // GCC extension begin #ifdef __STL_GTHREADS __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 } #else // GCC extension end # ifdef __STL_PTHREADS pthread_mutex_t _M_ref_count_lock; _Refcount_Base(_RC_t __n) : _M_ref_count(__n) { pthread_mutex_init(&_M_ref_count_lock, 0); } # elif defined(__STL_UITHREADS) mutex_t _M_ref_count_lock; _Refcount_Base(_RC_t __n) : _M_ref_count(__n) { mutex_init(&_M_ref_count_lock, USYNC_THREAD, 0); } # else _Refcount_Base(_RC_t __n) : _M_ref_count(__n) {} # endif // GCC extension begin #endif // GCC extension end // GCC extension begin #ifdef __STL_GTHREADS 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; } #else // GCC extension end // _M_incr and _M_decr # ifdef __STL_SGI_THREADS void _M_incr() { __add_and_fetch(&_M_ref_count, 1); } _RC_t _M_decr() { return __add_and_fetch(&_M_ref_count, (size_t) -1); } # elif defined (__STL_WIN32THREADS) void _M_incr() { InterlockedIncrement((_RC_t*)&_M_ref_count); } _RC_t _M_decr() { return InterlockedDecrement((_RC_t*)&_M_ref_count); } # elif defined(__STL_PTHREADS) void _M_incr() { pthread_mutex_lock(&_M_ref_count_lock); ++_M_ref_count; pthread_mutex_unlock(&_M_ref_count_lock); } _RC_t _M_decr() { pthread_mutex_lock(&_M_ref_count_lock); volatile _RC_t __tmp = --_M_ref_count; pthread_mutex_unlock(&_M_ref_count_lock); return __tmp; } # elif defined(__STL_UITHREADS) void _M_incr() { mutex_lock(&_M_ref_count_lock); ++_M_ref_count; mutex_unlock(&_M_ref_count_lock); } _RC_t _M_decr() { mutex_lock(&_M_ref_count_lock); /*volatile*/ _RC_t __tmp = --_M_ref_count; mutex_unlock(&_M_ref_count_lock); return __tmp; } # else /* No threads */ void _M_incr() { ++_M_ref_count; } _RC_t _M_decr() { return --_M_ref_count; } # endif // GCC extension begin #endif // GCC extension end }; // 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. // GCC extension begin #ifdef __STL_GTHREADS // We don't provide an _Atomic_swap in this configuration. This only // affects the use of ext/rope with threads. Someone could add this // later, if required. You can start by cloning the __STL_PTHREADS // path while making the obvious changes. Later it could be optimized // to use the atomicity.h abstraction layer from libstdc++-v3. #else // GCC extension end # ifdef __STL_SGI_THREADS inline unsigned long _Atomic_swap(unsigned long * __p, unsigned long __q) { # if __mips < 3 || !(defined (_ABIN32) || defined(_ABI64)) return test_and_set(__p, __q); # else return __test_and_set(__p, (unsigned long)__q); # endif } # elif defined(__STL_WIN32THREADS) inline unsigned long _Atomic_swap(unsigned long * __p, unsigned long __q) { return (unsigned long) InterlockedExchange((LPLONG)__p, (LONG)__q); } # elif defined(__STL_PTHREADS) // We use a template here only to get a unique initialized instance. template<int __dummy> struct _Swap_lock_struct { static pthread_mutex_t _S_swap_lock; }; template<int __dummy> pthread_mutex_t _Swap_lock_struct<__dummy>::_S_swap_lock = PTHREAD_MUTEX_INITIALIZER; // 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) { pthread_mutex_lock(&_Swap_lock_struct<0>::_S_swap_lock); unsigned long __result = *__p; *__p = __q; pthread_mutex_unlock(&_Swap_lock_struct<0>::_S_swap_lock); return __result; } # elif defined(__STL_UITHREADS) // We use a template here only to get a unique initialized instance. template<int __dummy> struct _Swap_lock_struct { static mutex_t _S_swap_lock; }; template<int __dummy> mutex_t _Swap_lock_struct<__dummy>::_S_swap_lock = DEFAULTMUTEX; // 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) { mutex_lock(&_Swap_lock_struct<0>::_S_swap_lock); unsigned long __result = *__p; *__p = __q; mutex_unlock(&_Swap_lock_struct<0>::_S_swap_lock); return __result; } # elif defined (__STL_SOLARIS_THREADS) // any better solutions ? // We use a template here only to get a unique initialized instance. template<int __dummy> struct _Swap_lock_struct { static mutex_t _S_swap_lock; }; # if ( __STL_STATIC_TEMPLATE_DATA > 0 ) template<int __dummy> mutex_t _Swap_lock_struct<__dummy>::_S_swap_lock = DEFAULTMUTEX; # else __DECLARE_INSTANCE(mutex_t, _Swap_lock_struct<__dummy>::_S_swap_lock, =DEFAULTMUTEX); # endif /* ( __STL_STATIC_TEMPLATE_DATA > 0 ) */ // 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) { mutex_lock(&_Swap_lock_struct<0>::_S_swap_lock); unsigned long __result = *__p; *__p = __q; mutex_unlock(&_Swap_lock_struct<0>::_S_swap_lock); return __result; } # else static inline unsigned long _Atomic_swap(unsigned long * __p, unsigned long __q) { unsigned long __result = *__p; *__p = __q; return __result; } # endif // GCC extension begin #endif // GCC extension end // 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. // Helper struct. This is a workaround for various compilers that don't // handle static variables in inline functions properly. template <int __inst> struct _STL_mutex_spin { enum { __low_max = 30, __high_max = 1000 }; // Low if we suspect uniprocessor, high for multiprocessor. static unsigned __max; static unsigned __last; }; template <int __inst> unsigned _STL_mutex_spin<__inst>::__max = _STL_mutex_spin<__inst>::__low_max; template <int __inst> unsigned _STL_mutex_spin<__inst>::__last = 0; // GCC extension begin #if defined(__STL_GTHREADS) #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 #endif // GCC extension end struct _STL_mutex_lock { // GCC extension begin #if defined(__STL_GTHREADS) // 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); } #else // GCC extension end #if defined(__STL_SGI_THREADS) || defined(__STL_WIN32THREADS) // It should be relatively easy to get this to work on any modern Unix. volatile unsigned long _M_lock; void _M_initialize() { _M_lock = 0; } static void _S_nsec_sleep(int __log_nsec) { # ifdef __STL_SGI_THREADS struct timespec __ts; /* Max sleep is 2**27nsec ~ 60msec */ __ts.tv_sec = 0; __ts.tv_nsec = 1L << __log_nsec; nanosleep(&__ts, 0); # elif defined(__STL_WIN32THREADS) if (__log_nsec <= 20) { Sleep(0); } else { Sleep(1 << (__log_nsec - 20)); } # else # error unimplemented # endif } void _M_acquire_lock() { volatile unsigned long* __lock = &this->_M_lock; if (!_Atomic_swap((unsigned long*)__lock, 1)) { return; } unsigned __my_spin_max = _STL_mutex_spin<0>::__max; unsigned __my_last_spins = _STL_mutex_spin<0>::__last; volatile unsigned __junk = 17; // Value doesn't matter. unsigned __i; for (__i = 0; __i < __my_spin_max; __i++) { if (__i < __my_last_spins/2 || *__lock) { __junk *= __junk; __junk *= __junk; __junk *= __junk; __junk *= __junk; continue; } if (!_Atomic_swap((unsigned long*)__lock, 1)) { // got it! // Spinning worked. Thus we're probably not being scheduled // against the other process with which we were contending. // Thus it makes sense to spin longer the next time. _STL_mutex_spin<0>::__last = __i; _STL_mutex_spin<0>::__max = _STL_mutex_spin<0>::__high_max; return; } } // We are probably being scheduled against the other process. Sleep. _STL_mutex_spin<0>::__max = _STL_mutex_spin<0>::__low_max; for (__i = 0 ;; ++__i) { int __log_nsec = __i + 6; if (__log_nsec > 27) __log_nsec = 27; if (!_Atomic_swap((unsigned long *)__lock, 1)) { return; } _S_nsec_sleep(__log_nsec); } } void _M_release_lock() { volatile unsigned long* __lock = &_M_lock; # if defined(__STL_SGI_THREADS) && defined(__GNUC__) && __mips >= 3 asm("sync"); *__lock = 0; # elif defined(__STL_SGI_THREADS) && __mips >= 3 \ && (defined (_ABIN32) || defined(_ABI64)) __lock_release(__lock); # else *__lock = 0; // This is not sufficient on many multiprocessors, since // writes to protected variables and the lock may be reordered. # endif } // We no longer use win32 critical sections. // They appear to be slower in the contention-free case, // and they appear difficult to initialize without introducing a race. #elif defined(__STL_PTHREADS) pthread_mutex_t _M_lock; void _M_initialize() { pthread_mutex_init(&_M_lock, NULL); } void _M_acquire_lock() { pthread_mutex_lock(&_M_lock); } void _M_release_lock() { pthread_mutex_unlock(&_M_lock); } #elif defined(__STL_UITHREADS) mutex_t _M_lock; void _M_initialize() { mutex_init(&_M_lock, USYNC_THREAD, 0); } void _M_acquire_lock() { mutex_lock(&_M_lock); } void _M_release_lock() { mutex_unlock(&_M_lock); } #else /* No threads */ void _M_initialize() {} void _M_acquire_lock() {} void _M_release_lock() {} #endif // GCC extension begin #endif // GCC extension end }; // GCC extension begin #if defined(__STL_GTHREADS) #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 #else // GCC extension end #ifdef __STL_PTHREADS // Pthreads locks must be statically initialized to something other than // the default value of zero. # define __STL_MUTEX_INITIALIZER = { PTHREAD_MUTEX_INITIALIZER } #elif defined(__STL_UITHREADS) // UIthreads locks must be statically initialized to something other than // the default value of zero. # define __STL_MUTEX_INITIALIZER = { DEFAULTMUTEX } #elif defined(__STL_SGI_THREADS) || defined(__STL_WIN32THREADS) # define __STL_MUTEX_INITIALIZER = { 0 } #else # define __STL_MUTEX_INITIALIZER #endif // GCC extension begin #endif // GCC extension end // 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 /* __SGI_STL_INTERNAL_THREADS_H */ // Local Variables: // mode:C++ // End: