diff --git a/ChangeLog b/ChangeLog
index 7b36bd732d..59e8feb40d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2016-03-04  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* sysdeps/x86_64/Makefile (sysdep_noprof): Add comments.
+
 2016-03-04  Amit Pawar  <Amit.Pawar@amd.com>
 	    H.J. Lu  <hongjiu.lu@intel.com>
 
diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
index 9fcadd8a57..788e4fc591 100644
--- a/sysdeps/x86_64/Makefile
+++ b/sysdeps/x86_64/Makefile
@@ -7,6 +7,9 @@ endif
 
 ifeq ($(subdir),gmon)
 sysdep_routines += _mcount
+# We cannot compile _mcount.S with -pg because that would create
+# recursive calls when ENTRY is used.  Just copy the normal static
+# object.
 sysdep_noprof += _mcount
 endif