Re: [PATCH] Kbuild: do not build dtbs concurrently

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 8/28/25 11:31 AM, Sascha Hauer wrote:
> commit 3c862a83f019 ("kbuild: restrict dtbs target to enabled DTs by
> default") added the dtbs target as a dependency to the images target.
> In the dtbs target we call into Kbuild for building the device trees.
> The device trees are also built as part of the regular build in
> parallel, so we end up running Kbuild for the same directory twice.
> 
> This sometimes results in failed builds with messages like this one
> (done with make V=2):
> 
>   AS [P]  arch/arm/dts/bcm2711-rpi-400.dtb.pbl.o - due to target missing
>   AS [P]  arch/arm/dts/bcm2711-rpi-400.dtb.pbl.o - due to target missing
> fixdep: error opening file: arch/arm/dts/.bcm2711-rpi-400.dtb.pbl.o.d: No such file or directory
> 
> Fix this by removing the dtbs target from the images dependencies. We
> then would no longer build the dtbs-list, so build that unconditionally
> once we descend into a directory containing device trees. The dtbs-list
> is built with always-y which should make sure it is ready once we need
> it in imagages/
> 
> Fixes: 3c862a83f019 ("kbuild: restrict dtbs target to enabled DTs by default")
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

> ---
>  Makefile               | 7 +------
>  scripts/Makefile.build | 2 +-
>  scripts/Makefile.dtbs  | 2 --
>  3 files changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index b9c252476f..7620c47cf4 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1187,15 +1187,10 @@ ifneq ($(dtstree),)
>  
>  PHONY += dtbs dtbs_prepare
>  dtbs: dtbs_prepare
> -	$(Q)$(MAKE) $(build)=$(dtstree) need-dtbslist=1
> +	$(Q)$(MAKE) $(build)=$(dtstree)
>  
>  dtbs_prepare: include/config/kernel.release scripts_dtc
>  
> -ifdef CONFIG_OFDEVICE
> -images: dtbs
> -images/%: dtbs
> -endif
> -
>  endif
>  
>  PHONY += scripts_dtc
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 591da3d750..fed8c247f9 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -56,7 +56,7 @@ ifneq ($(userprogs),)
>  include scripts/Makefile.userprogs
>  endif
>  
> -ifneq ($(need-dtbslist)$(dtb-y)$(dtb-)$(filter %.dtb %.dtb.o %.dtbo.o,$(targets)),)
> +ifneq ($(dtb-y)$(dtb-)$(filter %.dtb %.dtb.o %.dtbo.o,$(targets)),)
>  include $(srctree)/scripts/Makefile.dtbs
>  endif
>  
> diff --git a/scripts/Makefile.dtbs b/scripts/Makefile.dtbs
> index 7b5b9e1d16..25ed08e8ee 100644
> --- a/scripts/Makefile.dtbs
> +++ b/scripts/Makefile.dtbs
> @@ -10,11 +10,9 @@ always-y        += $(dtb-y)
>  # dtbs-list
>  # ---------------------------------------------------------------------------
>  
> -ifdef need-dtbslist
>  subdir-dtbslist := $(addsuffix /dtbs-list, $(subdir-ym))
>  dtb-y           += $(subdir-dtbslist)
>  always-y        += $(obj)/dtbs-list
> -endif
>  
>  $(subdir-dtbslist): $(obj)/%/dtbs-list: $(obj)/% ;
>  

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