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authorMasahiro Yamada <masahiroy@kernel.org>2021-04-25 09:24:07 +0300
committerMasahiro Yamada <masahiroy@kernel.org>2021-05-01 18:43:35 +0300
commit46b41d5dd8019b264717978c39c43313a524d033 (patch)
tree00e792005c14b5ad16f126dbec4e2f2201745505 /kernel
parent40cb020305f40bafc2a13c7e879a33dbbd607507 (diff)
downloadlinux-46b41d5dd8019b264717978c39c43313a524d033.tar.xz
kbuild: update config_data.gz only when the content of .config is changed
If the timestamp of the .config file is updated, config_data.gz is regenerated, then vmlinux is re-linked. This occurs even if the content of the .config has not changed at all. This issue was mitigated by commit 67424f61f813 ("kconfig: do not write .config if the content is the same"); Kconfig does not update the .config when it ends up with the identical configuration. The issue is remaining when the .config is created by *_defconfig with some config fragment(s) applied on top. This is typical for powerpc and mips, where several *_defconfig targets are constructed by using merge_config.sh. One workaround is to have the copy of the .config. The filechk rule updates the copy, kernel/config_data, by checking the content instead of the timestamp. With this commit, the second run with the same configuration avoids the needless rebuilds. $ make ARCH=mips defconfig all [ snip ] $ make ARCH=mips defconfig all *** Default configuration is based on target '32r2el_defconfig' Using ./arch/mips/configs/generic_defconfig as base Merging arch/mips/configs/generic/32r2.config Merging arch/mips/configs/generic/el.config Merging ./arch/mips/configs/generic/board-boston.config Merging ./arch/mips/configs/generic/board-ni169445.config Merging ./arch/mips/configs/generic/board-ocelot.config Merging ./arch/mips/configs/generic/board-ranchu.config Merging ./arch/mips/configs/generic/board-sead-3.config Merging ./arch/mips/configs/generic/board-xilfpga.config # # configuration written to .config # SYNC include/config/auto.conf CALL scripts/checksyscalls.sh CALL scripts/atomic/check-atomics.sh CHK include/generated/compile.h CHK include/generated/autoksyms.h Reported-by: Elliot Berman <eberman@codeaurora.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/.gitignore1
-rw-r--r--kernel/Makefile9
2 files changed, 8 insertions, 2 deletions
diff --git a/kernel/.gitignore b/kernel/.gitignore
index 4abc4e033ed8..dafdce3d18c5 100644
--- a/kernel/.gitignore
+++ b/kernel/.gitignore
@@ -1,2 +1,3 @@
# SPDX-License-Identifier: GPL-2.0-only
+/config_data
kheaders.md5
diff --git a/kernel/Makefile b/kernel/Makefile
index e8a6715f38dc..4df609be42d0 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -142,10 +142,15 @@ obj-$(CONFIG_SCF_TORTURE_TEST) += scftorture.o
$(obj)/configs.o: $(obj)/config_data.gz
-targets += config_data.gz
-$(obj)/config_data.gz: $(KCONFIG_CONFIG) FORCE
+targets += config_data config_data.gz
+$(obj)/config_data.gz: $(obj)/config_data FORCE
$(call if_changed,gzip)
+filechk_cat = cat $<
+
+$(obj)/config_data: $(KCONFIG_CONFIG) FORCE
+ $(call filechk,cat)
+
$(obj)/kheaders.o: $(obj)/kheaders_data.tar.xz
quiet_cmd_genikh = CHK $(obj)/kheaders_data.tar.xz