Stefan Fiedler:

package/base/glibc/glibc.conf

@@ -47,6 +47,16 @@ pkg_glibc_linuxthreads=1
 # fall back to linuxthreads for cross glibcs
 [ -n "$pkg_glibc_cross" ] && pkg_glibc_linuxthreads=1
 
+# Give a more descriptive error message than the one that would happen during the build.
+kernel_mainline="`uname -r | cut -f-2 -d'.'`"
+if [ $pkg_glibc_linuxthreads = 0 -a "$kernel_mainline" != "2.6" ] ; then
+	echo_error 'You are running a kernel of the $kernel_mainline series.'
+	echo_error 'Glibc with NPTL support cannot be built on $kernel_mainline kernels.'
+	echo_error 'Boot a 2.6 kernel to build Glibc with NPTL support or build Glibc'
+	echo_error 'with old threading support (linuxthreads) instead.'
+	abort
+fi
+
 #---------------------------------
 if [ $pkg_glibc_version = 22 ]; then