On Thu, 15 Mar 2018, Masahiro Yamada wrote:
> Commit d3fc425e819b ("kbuild: make sure autoksyms.h exists early")
> moved the code that touches autoksyms.h to scripts/kconfig/Makefile
> with obscure reason.
>
> From Nicolas' comment [1], he did not seem to be sure about the root
> cause.
>
> I guess I figured it out, so here is a fix-up I think is more correct.
> According to the error log in the original post [2], the build failed
> in scripts/mod/devicetable-offsets.c
>
> scripts/mod/Makefile is descended from scripts/Makefile, which is
> invoked from the top-level Makefile by the 'scripts' target.
>
> To build vmlinux and/or modules, Kbuild descend into $(vmlinux-dirs).
> This depends on 'prepare' and 'script' as follows:
>
> $(vmlinux-dirs): prepare scripts
>
> Because there is no dependency between 'prepare' and 'scripts', the
> parallel building can run them simultaneously.
>
> 'prepare' depends on 'prepare1', which touched autoksyms.h, whereas
> 'scripts' descends into script/, then scripts/mod/, which needed
> <generated/autoksyms.h> if CONFIG_TRIM_UNUSED_KSYMS. This was the
> reason of race.
>
> I am not happy to have unrelated code in the Kconfig Makefile, so
> getting it back to the top Makefile.
>
> I remove the standalone test target because I want to use it to
> create an empty autoksyms.h file. Here is a little improvement;
> unnecessary autoksyms.h is not created when CONFIG_TRIM_UNUSED_KSYMS
> is disabled.
>
> [1] https://lkml.org/lkml/2016/11/30/734
> [2] https://lkml.org/lkml/2016/11/30/531
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
You're the make master!
Acked-by: Nicolas Pitre <nico@xxxxxxxxxx>
> Commit:
>
> The discussion happened in Nov. 2016.
>
> I was not involved in it.
> I was not the Kbuild maintainer at that time.
>
> END
>
> ---
>
> Makefile | 12 +++++++-----
> scripts/kconfig/Makefile | 2 --
> 2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index fab0e19..decc870 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1010,9 +1010,11 @@ ifdef CONFIG_TRIM_UNUSED_KSYMS
> "$(MAKE) -f $(srctree)/Makefile vmlinux"
> endif
>
> -# standalone target for easier testing
> -include/generated/autoksyms.h: FORCE
> - $(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh true
> +autoksyms_h := $(if $(CONFIG_TRIM_UNUSED_KSYMS), include/generated/autoksyms.h)
> +
> +$(autoksyms_h):
> + $(Q)mkdir -p $(dir $@)
> + $(Q)touch $@
>
> ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
>
> @@ -1056,7 +1058,7 @@ include/config/kernel.release: include/config/auto.conf FORCE
> # in parallel
> PHONY += scripts
> scripts: scripts_basic include/config/auto.conf include/config/tristate.conf \
> - asm-generic gcc-plugins autoksyms
> + asm-generic gcc-plugins $(autoksyms_h)
> $(Q)$(MAKE) $(build)=$(@)
>
> # Things we need to do before we recursively start building the kernel
> @@ -1086,7 +1088,7 @@ endif
> # that need to depend on updated CONFIG_* values can be checked here.
> prepare2: prepare3 prepare-compiler-check outputmakefile asm-generic
>
> -prepare1: prepare2 $(version_h) include/generated/utsrelease.h \
> +prepare1: prepare2 $(version_h) $(autoksyms_h) include/generated/utsrelease.h \
> include/config/auto.conf
> $(cmd_crmodverdir)
>
> diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
> index cb3ec53..eb139a1 100644
> --- a/scripts/kconfig/Makefile
> +++ b/scripts/kconfig/Makefile
> @@ -38,8 +38,6 @@ nconfig: $(obj)/nconf
> # for external use.
> silentoldconfig: $(obj)/conf
> $(Q)mkdir -p include/config include/generated
> - $(Q)test -e include/generated/autoksyms.h || \
> - touch include/generated/autoksyms.h
> $< $(silent) --$@ $(Kconfig)
>
> localyesconfig localmodconfig: $(obj)/streamline_config.pl $(obj)/conf
> --
> 2.7.4
>
>
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