diff --git a/include/boost/detail/atomic_count.hpp b/include/boost/detail/atomic_count.hpp
index 6486755..d97fafa 100644
--- a/include/boost/detail/atomic_count.hpp
+++ b/include/boost/detail/atomic_count.hpp
@@ -72,6 +72,8 @@
 //      are called driven by smart_ptr interface...
 //
 
+//  Note: atomic_count_linux.hpp has been disabled by default; see the
+//        comments inside for more info.
 
 #include <boost/config.hpp>
 
@@ -90,17 +92,12 @@ typedef long atomic_count;
 }
 
 #elif defined(WIN32) || defined(_WIN32) || defined(__WIN32__)
-
-#include <boost/detail/atomic_count_win32.hpp>
-
-#elif defined(linux) || defined(__linux) || defined(__linux__)
-
-#include <boost/detail/atomic_count_linux.hpp>
-
+#  include <boost/detail/atomic_count_win32.hpp>
+//#elif defined(linux) || defined(__linux) || defined(__linux__)
+#elif defined(BOOST_USE_ASM_ATOMIC_H)
+#  include <boost/detail/atomic_count_linux.hpp>
 #elif defined(BOOST_HAS_PTHREADS)
-
-#include <boost/detail/atomic_count_pthreads.hpp>
-
+#  include <boost/detail/atomic_count_pthreads.hpp>
 #else
 
 // #warning Unrecognized platform, detail::atomic_count will not be thread safe
diff --git a/include/boost/detail/atomic_count_linux.hpp b/include/boost/detail/atomic_count_linux.hpp
index 8fd5346..1a69cec 100644
--- a/include/boost/detail/atomic_count_linux.hpp
+++ b/include/boost/detail/atomic_count_linux.hpp
@@ -13,7 +13,13 @@
 //
 
 //
-// On Linux, atomic.h is usually located in /usr/include/asm
+//  This implementation uses <asm/atomic.h>. This is a kernel header;
+//  using kernel headers in a user program may cause a number of problems,
+//  and not all flavors of Linux provide the atomic instructions.
+//
+//  This file is only provided because the performance of this implementation
+//  is significantly higher than the pthreads version. Use at your own risk
+//  (by defining BOOST_USE_ASM_ATOMIC_H.)
 //
 
 #include <asm/atomic.h>
diff --git a/include/boost/detail/lightweight_mutex.hpp b/include/boost/detail/lightweight_mutex.hpp
index 69a3a6c..d199114 100644
--- a/include/boost/detail/lightweight_mutex.hpp
+++ b/include/boost/detail/lightweight_mutex.hpp
@@ -31,6 +31,9 @@
 //  * Never keep a lightweight_mutex locked for long periods.
 //
 
+//  Note: lwm_linux.hpp has been disabled by default; see the comments
+//        inside for more info.
+
 
 #include <boost/config.hpp>
 
@@ -38,7 +41,8 @@
 #  include <boost/detail/lwm_nop.hpp>
 #elif defined(WIN32) || defined(_WIN32) || defined(__WIN32__)
 #  include <boost/detail/lwm_win32.hpp>
-#elif defined(linux) || defined(__linux) || defined(__linux__)
+//#elif defined(linux) || defined(__linux) || defined(__linux__)
+#elif defined(BOOST_USE_ASM_ATOMIC_H)
 #  include <boost/detail/lwm_linux.hpp>
 #elif defined(__sgi)
 #  include <boost/detail/lwm_irix.hpp>
diff --git a/include/boost/detail/lwm_linux.hpp b/include/boost/detail/lwm_linux.hpp
index f502d60..c4b3b1d 100644
--- a/include/boost/detail/lwm_linux.hpp
+++ b/include/boost/detail/lwm_linux.hpp
@@ -16,6 +16,16 @@
 //  warranty, and with no claim as to its suitability for any purpose.
 //
 
+//
+//  This implementation uses <asm/atomic.h>. This is a kernel header;
+//  using kernel headers in a user program may cause a number of problems,
+//  and not all flavors of Linux provide the atomic instructions.
+//
+//  This file is only provided because the performance of this implementation
+//  is about 3.5 times higher than the pthreads version. Use at your own risk
+//  (by defining BOOST_USE_ASM_ATOMIC_H.)
+//
+
 #include <asm/atomic.h>
 #include <sched.h>