kbuild: deb-pkg: build binary-arch in parallel

'make deb-pkg' builds build-arch in parallel, but binary-arch serially.

Given that all binary packages are independent of one another, they can
be built in parallel.

I am uncertain whether debian/files is robust against a race condition.
Just in case, make dh_gencontrol (dpkg-gencontrol) output to separate
debian/*.files, which are then concatenated into debian/files.

Signed-off-by: Masahiro Yamada <[e-mail]>
Reviewed-by: Nicolas Schier <[e-mail]>

scripts/package/builddeb

···
 	fi
 }
 
-create_package() {
-	export DH_OPTIONS="-p${1}"
-
-	dh_installdocs
-	dh_installchangelogs
-	dh_compress
-	dh_fixperms
-	dh_gencontrol
-	dh_md5sums
-	dh_builddeb -- ${KDEB_COMPRESS:+-Z$KDEB_COMPRESS}
-}
-
 install_linux_image () {
 	pname=$1
 	pdir=debian/$1
···
 	mv "$pdir/usr/include/asm" "$pdir/usr/include/${DEB_HOST_MULTIARCH}"
 }
 
-rm -f debian/files
+package=$1
 
-packages_enabled=$(dh_listpackages)
-
-for package in ${packages_enabled}
-do
-	case ${package} in
-	*-dbg)
-		install_linux_image_dbg "${package}";;
-	linux-image-*|user-mode-linux-*)
-		install_linux_image "${package}";;
-	linux-libc-dev)
-		install_libc_headers "${package}";;
-	linux-headers-*)
-		install_kernel_headers "${package}";;
-	esac
-	create_package "${package}"
-done
+case "${package}" in
+*-dbg)
+	install_linux_image_dbg "${package}";;
+linux-image-*|user-mode-linux-*)
+	install_linux_image "${package}";;
+linux-libc-dev)
+	install_libc_headers "${package}";;
+linux-headers-*)
+	install_kernel_headers "${package}";;
+esac

scripts/package/debian/rules

···
 CROSS_COMPILE ?= $(filter-out $(DEB_BUILD_GNU_TYPE)-, $(DEB_HOST_GNU_TYPE)-)
 make-opts = ARCH=$(ARCH) KERNELRELEASE=$(KERNELRELEASE) KBUILD_BUILD_VERSION=$(revision) $(addprefix CROSS_COMPILE=,$(CROSS_COMPILE))
 
+binary-targets := $(addprefix binary-, image image-dbg headers libc-dev)
+
+all-packages = $(shell dh_listpackages)
+image-package = $(filter linux-image-% user-%, $(filter-out %-dbg, $(all-packages)))
+image-dbg-package = $(filter %-dbg, $(all-packages))
+libc-dev-package = $(filter linux-libc-dev, $(all-packages))
+headers-package = $(filter linux-headers-%, $(all-packages))
+
+mk-files = $(patsubst binary-%,debian/%.files,$1)
+package = $($(@:binary-%=%-package))
+
+# DH_OPTION is an environment variable common for all debhelper commands.
+# We could 'export' it, but here it is passed from the command line to clarify
+# which package is being processed in the build log.
+DH_OPTIONS = -p$(package)
+
+define binary
+	$(Q)+$(MAKE) $(make-opts) run-command KBUILD_RUN_COMMAND='+$$(srctree)/scripts/package/builddeb $(package)'
+	$(Q)dh_installdocs $(DH_OPTIONS)
+	$(Q)dh_installchangelogs $(DH_OPTIONS)
+	$(Q)dh_compress $(DH_OPTIONS)
+	$(Q)dh_fixperms $(DH_OPTIONS)
+	$(Q)dh_gencontrol $(DH_OPTIONS) -- -f$(call mk-files,$@)
+	$(Q)dh_md5sums $(DH_OPTIONS)
+	$(Q)dh_builddeb $(DH_OPTIONS) -- $(addprefix -Z,$(KDEB_COMPRESS))
+endef
+
+.PHONY: $(binary-targets)
+$(binary-targets): build-arch
+	$(Q)truncate -s0 $(call mk-files,$@)
+	$(if $(package),$(binary))
+
 .PHONY: binary binary-indep binary-arch
 binary: binary-arch binary-indep
 binary-indep: build-indep
-binary-arch: build-arch
-	$(Q)$(MAKE) $(make-opts) \
-	run-command KBUILD_RUN_COMMAND='+$$(srctree)/scripts/package/builddeb'
+binary-arch: $(binary-targets)
+	$(Q)cat $(call mk-files,$^) > debian/files
 
 .PHONY: build build-indep build-arch
 build: build-arch build-indep
···
 
 .PHONY: clean
 clean:
-	$(Q)rm -rf debian/files debian/linux-* debian/deb-env.vars*
+	$(Q)rm -rf debian/files debian/linux-* debian/deb-env.vars* debian/*.files
 	$(Q)$(MAKE) ARCH=$(ARCH) clean
 
 # If DEB_HOST_ARCH is empty, it is likely that debian/rules was executed