boost/detail/lightweight_mutex.hpp
#ifndef BOOST_DETAIL_LIGHTWEIGHT_MUTEX_HPP_INCLUDED #define BOOST_DETAIL_LIGHTWEIGHT_MUTEX_HPP_INCLUDED // MS compatible compilers support #pragma once #if defined(_MSC_VER) && (_MSC_VER >= 1020) # pragma once #endif // // boost/detail/lightweight_mutex.hpp - lightweight mutex // // Copyright (c) 2002, 2003 Peter Dimov and Multi Media Ltd. // // Permission to copy, use, modify, sell and distribute this software // is granted provided this copyright notice appears in all copies. // This software is provided "as is" without express or implied // warranty, and with no claim as to its suitability for any purpose. // // typedef <unspecified> boost::detail::lightweight_mutex; // // boost::detail::lightweight_mutex meets a subset of the Mutex concept // requirements: http://www.boost.org/libs/thread/doc/mutex_concept.html#Mutex // // * Used by the smart pointer library // * Performance oriented // * Header-only implementation // * Small memory footprint // * Not a general purpose mutex, use boost::mutex, CRITICAL_SECTION or // pthread_mutex instead. // * Never spin in a tight lock/do-something/unlock loop, since // lightweight_mutex does not guarantee fairness. // * Never keep a lightweight_mutex locked for long periods. // // The current implementation can use a pthread_mutex, a CRITICAL_SECTION, // or a platform-specific spinlock. // // You can force a particular implementation by defining BOOST_LWM_USE_PTHREADS, // BOOST_LWM_USE_CRITICAL_SECTION, or BOOST_LWM_USE_SPINLOCK. // // If neither macro has been defined, the default is to use a spinlock on Win32, // and a pthread_mutex otherwise. // // Note that a spinlock is not a general synchronization primitive. In particular, // it is not guaranteed to be a memory barrier, and it is possible to "livelock" // if a lower-priority thread has acquired the spinlock but a higher-priority // thread is spinning trying to acquire the same lock. // // For these reasons, spinlocks have been disabled by default except on Windows, // where a spinlock can be several orders of magnitude faster than a CRITICAL_SECTION. // Note: lwm_linux.hpp has been disabled by default; see the comments // inside for more info. #include <boost/config.hpp> // Note to implementors: if you write a platform-specific spinlock // for a platform that supports pthreads, be sure to test its performance // against the pthreads-based version using shared_ptr_timing_test.cpp and // shared_ptr_mt_test.cpp. Custom versions are usually not worth the trouble // _unless_ the performance gains are substantial. // // Be sure to compare against a "real" pthreads library; // shared_ptr_timing_test.cpp will compile succesfully with a stub do-nothing // pthreads library, since it doesn't create any threads. #if (defined(WIN32) || defined(_WIN32) || defined(__WIN32__)) && !defined(BOOST_LWM_USE_CRITICAL_SECTION) && !defined(BOOST_LWM_USE_PTHREADS) # define BOOST_LWM_WIN32 #endif #if !defined(BOOST_HAS_THREADS) # if defined(BOOST_LWM_WIN32) # include <boost/detail/lwm_win32_nt.hpp> # else # include <boost/detail/lwm_nop.hpp> # endif #elif defined(BOOST_LWM_USE_SPINLOCK) && defined(BOOST_USE_ASM_ATOMIC_H) # include <boost/detail/lwm_linux.hpp> #elif defined(BOOST_LWM_USE_CRITICAL_SECTION) # include <boost/detail/lwm_win32_cs.hpp> #elif defined(BOOST_LWM_USE_PTHREADS) # include <boost/detail/lwm_pthreads.hpp> #elif defined(BOOST_LWM_WIN32) # include <boost/detail/lwm_win32.hpp> #elif defined(BOOST_LWM_USE_SPINLOCK) && defined(__sgi) # include <boost/detail/lwm_irix.hpp> #elif defined(BOOST_LWM_USE_SPINLOCK) && defined(__GLIBCPP__) # include <boost/detail/lwm_gcc.hpp> #elif defined(BOOST_HAS_PTHREADS) # define BOOST_LWM_USE_PTHREADS # include <boost/detail/lwm_pthreads.hpp> #else // Use #define BOOST_DISABLE_THREADS to avoid the error # error Unrecognized threading platform #endif #endif // #ifndef BOOST_DETAIL_LIGHTWEIGHT_MUTEX_HPP_INCLUDED