Re: Parallel building of Linux Kernel is broken

[Paul Smith]

On Thu, 2018-07-12 at 10:26 +0900, Masahiro Yamada wrote:
> $ make -j8 defconfig all
>   HOSTCC  scripts/basic/fixdep
>   HOSTCC  scripts/kconfig/conf.o
>   YACC    scripts/kconfig/zconf.tab.c
>   LEX     scripts/kconfig/zconf.lex.c
>   HOSTCC  scripts/kconfig/zconf.tab.o
>   HOSTLD  scripts/kconfig/conf
> *** Default configuration is based on 'x86_64_defconfig'
> #
> # configuration written to .config
> #
> scripts/kconfig/conf  --syncconfig Kconfig
> make[1]: warning: jobserver unavailable: using -j1.  Add '+' to
> parent
> make rule.
>   SYSTBL  arch/x86/include/generated/asm/syscalls_32.h

Someone will need to investigate this further as the information we
need has been elided.  Is there a way to invoke the Linux kernel
makefile with a "verbose" mode that doesn't use these shorthand outputs
for commands but instead actually shows the commands that recipes ask
make to invoke?  That's what we need to see; the actual command that
was used to recursively invoke make.

This warning means that a sub-make has been invoked but that the
makefile invoking it didn't realize it was a sub-make: that was hidden
from make by not using the $(MAKE) variable in the recipe.

In that case, make recommends that the makefile rule be prefixed with
the '+' character to tell make that the rule is a recursive invocation.

Unless make realizes that the recipe it runs will invoke a sub-make, it
can't properly prepare the environment for that sub-make.

I'm somewhat surprised that the build was not seeing this error before,
because it definitely was previously emitted: that error message has
been around for a long time.

As mentioned I'd need to see the actual command line invocation in
order to understand why this might have happened.