Re: [Buildroot] [PATCH] linux/linux.mk: forcibly (re)enable Make jobserver

On 30/07/2026 20:06, Laszlo Ersek wrote:
> Commit 0b9efc991f8a («linux: use BR2_MAKE», 2023-04-10) replaced $(MAKE)
> with $(BR2_MAKE) in a number of recipes. As a consequence, the child make
> is unable to discover the job server, and we get a warning such as
> 
>> warning: jobserver unavailable: using -j1. Add `+' to parent make rule.
> 
> https://www.gnu.org/software/make/manual/html_node/Error-Messages.html
> https://www.gnu.org/software/make/manual/html_node/MAKE-Variable.html
> 
> Inform the parent Make, by prefixing the recipe with "+", that $(BR2_MAKE)
> can deal with the job server.
> 
> Cc: Arnout Vandecappelle <[email protected]>
> Cc: Oleg Lyovin <[email protected]>
> Cc: [email protected]
> Signed-off-by: Laszlo Ersek <[email protected]>
> ---
> 
> Notes:
>      Commit 0b9efc991f8a replaces multiple instances of $(MAKE) with
>      $(BR2_MAKE); I'm only prefixing the one recipe with "+" that seems to
>      cause the most noticeable slowdown for me (by missing out on a parallel
>      kernel build).

  Are you really sure this speeds things up? The core of the work should be in 
the `make all` invocation on line 546. All the other invocations should be 
pretty much serial. In particular the rebuild-with-initramfs should do nothing 
more than re-linking and re-compressing the kernel because the exact same 
command was already done in the build step.

  Regards,
  Arnout


>   linux/linux.mk | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/linux/linux.mk b/linux/linux.mk
> index e790daff6608..80581081a7eb 100644
> --- a/linux/linux.mk
> +++ b/linux/linux.mk
> @@ -696,7 +696,7 @@ linux-rebuild-with-initramfs: rootfs-cpio
>   linux-rebuild-with-initramfs:
>   	@$(call MESSAGE,"Rebuilding kernel with initramfs")
>   	# Build the kernel.
> -	$(LINUX_MAKE_ENV) $(BR2_MAKE) $(LINUX_MAKE_FLAGS) -C $(LINUX_DIR) $(LINUX_TARGET_NAME)
> +	+$(LINUX_MAKE_ENV) $(BR2_MAKE) $(LINUX_MAKE_FLAGS) -C $(LINUX_DIR) $(LINUX_TARGET_NAME)
>   	$(LINUX_APPEND_DTB)
>   	# Copy the kernel image(s) to its(their) final destination
>   	$(call LINUX_INSTALL_IMAGE,$(BINARIES_DIR))
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