From: Masahiro Yamada <masahiroy@kernel.org>
To: linux-kbuild@vger.kernel.org
Cc: Masahiro Yamada <masahiroy@kernel.org>,
Elliot Berman <eberman@codeaurora.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH 5/5] kbuild: update config_data.gz only when the content of .config is changed
Date: Sun, 25 Apr 2021 15:24:07 +0900 [thread overview]
Message-ID: <20210425062407.1183801-5-masahiroy@kernel.org> (raw)
In-Reply-To: <20210425062407.1183801-1-masahiroy@kernel.org>
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 actually not changed.
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 (ab)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>
---
kernel/.gitignore | 1 +
kernel/Makefile | 9 +++++++--
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/kernel/.gitignore b/kernel/.gitignore
index 4dc1ffe9770b..c6b299a6b786 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 320f1f3941b7..605ec3e70cb7 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -138,10 +138,15 @@ 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
--
2.27.0
next prev parent reply other threads:[~2021-04-25 6:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-25 6:24 [PATCH 1/5] kernel/.gitgnore: remove stale timeconst.h and hz.bc Masahiro Yamada
2021-04-25 6:24 ` [PATCH 2/5] .gitignore: move tags and TAGS close to other tag files Masahiro Yamada
2021-04-25 6:24 ` [PATCH 3/5] .gitignore: ignore only top-level modules.builtin Masahiro Yamada
2021-04-25 6:24 ` [PATCH 4/5] .gitignore: prefix local generated files with a slash Masahiro Yamada
2021-04-26 10:50 ` Miguel Ojeda
2021-04-26 15:33 ` Rob Herring
2021-04-26 18:55 ` Paraschiv, Andra-Irina
2021-04-25 6:24 ` Masahiro Yamada [this message]
2021-05-05 17:48 ` [PATCH 1/5] kernel/.gitgnore: remove stale timeconst.h and hz.bc Masahiro Yamada
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