#ifndef BOOST_DETAIL_LIGHTWEIGHT_MUTEX_HPP_INCLUDED
#define BOOST_DETAIL_LIGHTWEIGHT_MUTEX_HPP_INCLUDED
-#if _MSC_VER >= 1020
-#pragma once
+// 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 Peter Dimov and Multi Media Ltd.
+// 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.
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
//
// 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.
+// boost::detail::lightweight_mutex is a header-only implementation of
+// a subset of the Mutex concept requirements:
//
-// You can force a particular implementation by defining BOOST_LWM_USE_PTHREADS,
-// BOOST_LWM_USE_CRITICAL_SECTION, or BOOST_LWM_USE_SPINLOCK.
+// http://www.boost.org/doc/html/threads/concepts.html#threads.concepts.Mutex
//
-// If neither macro has been defined, the default is to use a spinlock on Win32,
-// and a pthread_mutex otherwise.
+// It maps to a CRITICAL_SECTION on Windows or a pthread_mutex on POSIX.
//
-// 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.
-
-#ifndef BOOST_HAS_THREADS
-# include <boost/detail/lwm_nop.hpp>
-#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>
+#if !defined(BOOST_HAS_THREADS)
+# include <boost/detail/lwm_nop.hpp>
#elif defined(WIN32) || defined(_WIN32) || defined(__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>
+# include <boost/detail/lwm_win32_cs.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