Enable lock elision again on s390 and s390x

glibc.spec

@@ -23,6 +23,15 @@
 # to provide a more optimized version of the package for your arch.
 %define auxarches athlon alphaev6
 ##############################################################################
+# Enable lock elision support for these architectures
+#
+# At the moment lock elision is disabled on x86_64 until there's a CPU that
+# would actually benefit from enabling it.  Intel released a microcode update
+# to disable HLE and RTM at boot and the Fedora kernel now applies it early
+# enough that keeping lock elision enabled should be harmless, but we have
+# disabled it anyway as a conservative measure.
+%define lock_elision_arches s390 s390x
+##############################################################################
 # We build a special package for Xen that includes TLS support with
 # no negative segment offsets for use with Xen guests. This is
 # purely an optimization for increased performance on those arches.
@@ -698,11 +707,6 @@ build()
 	build_CFLAGS="$BuildFlags -g -O3 $*"
 	# Some configure checks can spuriously fail for some architectures if
 	# unwind info is present
-	#
-	# At the moment lock elision is temporarily disabled until we work
-	# out how to update the microcode in early boot to prevent the cpuid
-	# results from becoming stale. Once this is fixed add back:
-	#		--enable-lock-elision \
 	configure_CFLAGS="$build_CFLAGS -fno-asynchronous-unwind-tables"
 	../configure CC="$GCC" CXX="$GXX" CFLAGS="$configure_CFLAGS" \
 		--prefix=%{_prefix} \
@@ -718,6 +722,9 @@ build()
 %endif
 %ifarch ppc64p7
 		--with-cpu=power7 \
+%endif
+%ifarch %{lock_elision_arches}
+		--enable-lock-elision \
 %endif
 		--disable-profile --enable-nss-crypt ||
 		{ cat config.log; false; }
@@ -1728,6 +1735,7 @@ rm -f *.filelist*
 %changelog
 * Tue Sep 30 2014 Siddhesh Poyarekar <siddhesh@redhat.com> - 2.20.90-6
 - Disable more Intel TSX usage in rwlocks (#1146967).
+- Enable lock elision again on s390 and s390x.
 
 * Fri Sep 26 2014 Carlos O'Donell <carlos@redhat.com> - 2.20.90-5
 - Disable lock elision support for Intel hardware until microcode