//
// 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
+// boost::detail::lightweight_mutex is a header-only implementation of
+// a subset of the Mutex concept requirements:
//
-// * 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.
+// http://www.boost.org/doc/html/threads/concepts.html#threads.concepts.Mutex
//
-// The current implementation can use a pthread_mutex, a CRITICAL_SECTION,
-// or a platform-specific spinlock.
+// It maps to a CRITICAL_SECTION on Windows or a pthread_mutex on POSIX.
//
-// 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_nop.hpp>
+#elif defined(WIN32) || defined(_WIN32) || defined(__WIN32__)
# 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