Step 3 of the switch to support configuration with NPTL:

Change "configure.in".

The branches for Tru64 (ex: OSF/1) and Linux are separated,
and for Linux 'getconf GNU_LIBPTHREAD_VERSION' is used to tell between Linuxthreads and NPTL.

configure.in

@@ -411,12 +411,12 @@ if expr "$target_os" : "[[Ll]]inux.*" > /dev/null
 then
   MYSQLD_DEFAULT_SWITCHES="--skip-locking"
   TARGET_LINUX="true"
-  AC_MSG_RESULT("yes");
+  AC_MSG_RESULT("yes")
   AC_DEFINE([TARGET_OS_LINUX], [1], [Whether we build for Linux])
 else
   MYSQLD_DEFAULT_SWITCHES=""
   TARGET_LINUX="false"
-  AC_MSG_RESULT("no");
+  AC_MSG_RESULT("no")
 fi
 AC_SUBST(MYSQLD_DEFAULT_SWITCHES)
 AC_SUBST(TARGET_LINUX)
@@ -1267,11 +1267,36 @@ esac
 # We have to check libc last because else it fails on Solaris 2.6
 
 with_posix_threads="no"
-# Hack for DEC-UNIX (OSF1)
+# Search thread lib on Linux
 if test "$with_named_thread" = "no" -a "$with_mit_threads" = "no"
 then
+    AC_MSG_CHECKING("Linux threads")
+    if test "$TARGET_LINUX" = "true"
+    then
+        AC_MSG_RESULT("starting")
+        # use getconf to check glibc contents
+        AC_MSG_CHECKING("getconf GNU_LIBPTHREAD_VERSION")
+        case `getconf GNU_LIBPTHREAD_VERSION | tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ` in
+        NPTL* )
+                AC_MSG_RESULT("NPTL")
+                AC_DEFINE([HAVE_NPTL], [1], [NPTL threads implementation])
+                with_named_thread="-lpthread"
+                ;;
+        LINUXTHREADS* )
+                AC_MSG_RESULT("Linuxthreads")
+                AC_DEFINE([HAVE_LINUXTHREADS], [1], 
+                      [Whether we are using Xavier Leroy's LinuxThreads])
+                with_named_thread="-lpthread"
+                ;;
+        * )
+                AC_MSG_RESULT("unknown")
+                ;;
+        esac
+        if test "$with_named_thread" = "no"
+        then
+          # old method, check headers
           # Look for LinuxThreads.
-  AC_MSG_CHECKING("LinuxThreads")
+          AC_MSG_CHECKING("LinuxThreads in header file comment")
           res=`grep Linuxthreads /usr/include/pthread.h 2>/dev/null | wc -l`
           if test "$res" -gt 0
           then
@@ -1287,41 +1312,48 @@ then
           else
             AC_MSG_RESULT("Not found")
             # If this is a linux machine we should barf
-      if test "$TARGET_LINUX" = "true"
-      then
-	AC_MSG_ERROR([This is a linux system and Linuxthreads was not
-found. On linux Linuxthreads should be used.  Please install Linuxthreads
-(or a new glibc) and try again.  See the Installation chapter in the
-Reference Manual for more information.])
+            AC_MSG_ERROR([This is a Linux system without a working getconf, 
+and Linuxthreads was not found. Please install it (or a new glibc) and try again.  
+See the Installation chapter in the Reference Manual for more information.])
+          fi
+        else
+            AC_MSG_RESULT("no need to check headers")
+        fi
+        
+        AC_MSG_CHECKING("for pthread_create in -lpthread");
+        ac_save_LIBS="$LIBS"
+        LIBS="$LIBS -lpthread"
+        AC_TRY_LINK( [#include <pthread.h>],
+              [ (void) pthread_create((pthread_t*) 0,(pthread_attr_t*) 0, 0, 0); ],
+              AC_MSG_RESULT("yes"),
+              [ AC_MSG_RESULT("no")
+                AC_MSG_ERROR([
+This is a Linux system claiming to support threads, either Linuxthreads or NPTL, but linking a test program failed.  
+Please install one of these (or a new glibc) and try again.  
+See the Installation chapter in the Reference Manual for more information.]) ]
+              )
+        LIBS="$ac_save_LIBS"
     else
-	AC_MSG_CHECKING("DEC threads")
+        AC_MSG_RESULT("no")
+    fi  # "$TARGET_LINUX" 
+fi  # "$with_named_thread" = "no" -a "$with_mit_threads" = "no"
+
+
+# Hack for DEC-UNIX (OSF1 -> Tru64)
+if test "$with_named_thread" = "no" -a "$with_mit_threads" = "no"
+then
+    AC_MSG_CHECKING("DEC threads post OSF/1 3.2")
     if test -f /usr/shlib/libpthread.so -a -f /usr/lib/libmach.a -a -f /usr/ccs/lib/cmplrs/cc/libexc.a
     then
       with_named_thread="-lpthread -lmach -lexc"
       CFLAGS="$CFLAGS -D_REENTRANT"
       CXXFLAGS="$CXXFLAGS -D_REENTRANT"
-	  AC_DEFINE(HAVE_DEC_THREADS, [1],
-                    [Whether we are using DEC threads])
-	  AC_MSG_RESULT("yes")
-	else
-	  AC_MSG_RESULT("no")
-	  AC_MSG_CHECKING("DEC 3.2 threads")
-          if test -f /usr/shlib/libpthreads.so -a -f /usr/lib/libmach.a -a -f /usr/ccs/lib/cmplrs/cc/libexc.a
-	  then
-	    with_named_thread="-lpthreads -lmach -lc_r"
-	    AC_DEFINE(HAVE_DEC_THREADS, [1])
-            AC_DEFINE([HAVE_DEC_3_2_THREADS], [1],
-                      [Whether we are using OSF1 DEC threads on 3.2])
-            with_osf32_threads="yes"
-            MYSQLD_DEFAULT_SWITCHES="--skip-thread-priority"
+      AC_DEFINE(HAVE_DEC_THREADS, [1], [Whether we are using DEC threads])
       AC_MSG_RESULT("yes")
     else
       AC_MSG_RESULT("no")
-          fi
-	fi
-     fi
-   fi
-fi
+    fi  # DEC threads
+fi  # "$with_named_thread" = "no" -a "$with_mit_threads" = "no"
 
 
 dnl This is needed because -lsocket has to come after the thread