kbuild: update modules.order only when contained modules are updated
Make modules.order depend on $(obj-m), and use if_changed to build it.
This will avoid unneeded update of modules.order, which will be useful
to optimize the modpost stage.
Currently, the second pass of modpost is always invoked. By checking the
timestamp of modules.order, we can avoid the unneeded modpost.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
diff --git a/Makefile b/Makefile
index 24cf37c..b0bbf84 100644
--- a/Makefile
+++ b/Makefile
@@ -1066,6 +1066,10 @@
$(patsubst %/,%,$(filter %/, $(core-) \
$(drivers-) $(libs-))))
+subdir-modorder := $(addsuffix modules.order,$(filter %/, \
+ $(core-y) $(core-m) $(libs-y) $(libs-m) \
+ $(drivers-y) $(drivers-m)))
+
build-dirs := $(vmlinux-dirs)
clean-dirs := $(vmlinux-alldirs)
@@ -1124,7 +1128,7 @@
# The actual objects are generated when descending,
# make sure no implicit rule kicks in
-$(sort $(vmlinux-deps)): descend ;
+$(sort $(vmlinux-deps) $(subdir-modorder)): descend ;
filechk_kernel.release = \
echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"
@@ -1345,8 +1349,12 @@
modules_check: modules.order
$(Q)$(CONFIG_SHELL) $(srctree)/scripts/modules-check.sh $<
-modules.order: descend
- $(Q)$(AWK) '!x[$$0]++' $(addsuffix /$@, $(build-dirs)) > $@
+cmd_modules_order = $(AWK) '!x[$$0]++' $(real-prereqs) > $@
+
+modules.order: $(subdir-modorder) FORCE
+ $(call if_changed,modules_order)
+
+targets += modules.order
# Target to prepare building external modules
PHONY += modules_prepare