[4/7] kbuild: restore touching autoksyms.h to the top Makefile

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@socionext.com>

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(-)

-- 
2.7.4

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@socionext.com>


You're the make master!

Acked-by: Nicolas Pitre <nico@linaro.org>




> 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

> 

>