[1/3] um: fix parallel building with O= option
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Message ID 1533358023-5801-2-git-send-email-yamada.masahiro@socionext.com
State Not Applicable
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Series
  • Kbuild: fix and clean-up arch/um/Makefile
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Commit Message

Masahiro Yamada Aug. 4, 2018, 4:47 a.m. UTC
Randy Dunlap reports UML occasionally fails to build with -j<N> and
O=<builddir> options.

  make[1]: Entering directory '/home/rdunlap/mmotm-2018-0802-1529/UM64'
    UPD     include/generated/uapi/linux/version.h
    WRAP    arch/x86/include/generated/asm/dma-contiguous.h
    WRAP    arch/x86/include/generated/asm/export.h
    WRAP    arch/x86/include/generated/asm/early_ioremap.h
    WRAP    arch/x86/include/generated/asm/mcs_spinlock.h
    WRAP    arch/x86/include/generated/asm/mm-arch-hooks.h
    WRAP    arch/x86/include/generated/uapi/asm/bpf_perf_event.h
    WRAP    arch/x86/include/generated/uapi/asm/poll.h
    GEN     ./Makefile
  make[2]: *** No rule to make target 'archheaders'.  Stop.
  arch/um/Makefile:119: recipe for target 'archheaders' failed
  make[1]: *** [archheaders] Error 2
  make[1]: *** Waiting for unfinished jobs....
    UPD     include/config/kernel.release
  make[1]: *** wait: No child processes.  Stop.
  Makefile:146: recipe for target 'sub-make' failed
  make: *** [sub-make] Error 2

The cause of the problem is the use of '$(MAKE) KBUILD_SRC=',
which recurses to the top Makefile via the $(objtree)/Makefile
generated by scripts/mkmakefile.

When you run "make -j<N> O=<builddir> ARCH=um", Make can execute
'archheaders' and 'outputmakefile' targets simultaneously because
there is no dependency between them.

If it happens,

  $(Q)$(MAKE) KBUILD_SRC= ARCH=$(HEADER_ARCH) archheaders

... tries to run $(objtree)/Makefile that is being updated.

The correct way for the recursion is

  $(Q)$(MAKE) -f $(srctree)/Makefile ARCH=$(HEADER_ARCH) archheaders

..., which does not rely on the generated Makefile.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 arch/um/Makefile | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Comments

Masahiro Yamada Aug. 4, 2018, 4:51 a.m. UTC | #1
2018-08-04 13:47 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
> Randy Dunlap reports UML occasionally fails to build with -j<N> and
> O=<builddir> options.
>
>   make[1]: Entering directory '/home/rdunlap/mmotm-2018-0802-1529/UM64'
>     UPD     include/generated/uapi/linux/version.h
>     WRAP    arch/x86/include/generated/asm/dma-contiguous.h
>     WRAP    arch/x86/include/generated/asm/export.h
>     WRAP    arch/x86/include/generated/asm/early_ioremap.h
>     WRAP    arch/x86/include/generated/asm/mcs_spinlock.h
>     WRAP    arch/x86/include/generated/asm/mm-arch-hooks.h
>     WRAP    arch/x86/include/generated/uapi/asm/bpf_perf_event.h
>     WRAP    arch/x86/include/generated/uapi/asm/poll.h
>     GEN     ./Makefile
>   make[2]: *** No rule to make target 'archheaders'.  Stop.
>   arch/um/Makefile:119: recipe for target 'archheaders' failed
>   make[1]: *** [archheaders] Error 2
>   make[1]: *** Waiting for unfinished jobs....
>     UPD     include/config/kernel.release
>   make[1]: *** wait: No child processes.  Stop.
>   Makefile:146: recipe for target 'sub-make' failed
>   make: *** [sub-make] Error 2
>
> The cause of the problem is the use of '$(MAKE) KBUILD_SRC=',
> which recurses to the top Makefile via the $(objtree)/Makefile
> generated by scripts/mkmakefile.
>
> When you run "make -j<N> O=<builddir> ARCH=um", Make can execute
> 'archheaders' and 'outputmakefile' targets simultaneously because
> there is no dependency between them.
>
> If it happens,
>
>   $(Q)$(MAKE) KBUILD_SRC= ARCH=$(HEADER_ARCH) archheaders
>
> ... tries to run $(objtree)/Makefile that is being updated.
>
> The correct way for the recursion is
>
>   $(Q)$(MAKE) -f $(srctree)/Makefile ARCH=$(HEADER_ARCH) archheaders
>
> ..., which does not rely on the generated Makefile.
>



I forgot to add this:

Reported-by: Randy Dunlap <rdunlap@infradead.org>




> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
>
>  arch/um/Makefile | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/um/Makefile b/arch/um/Makefile
> index e54dda8..de340e4 100644
> --- a/arch/um/Makefile
> +++ b/arch/um/Makefile
> @@ -122,8 +122,7 @@ archheaders:
>         $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.asm-generic \
>                     kbuild-file=$(HOST_DIR)/include/uapi/asm/Kbuild \
>                     obj=$(HOST_DIR)/include/generated/uapi/asm
> -       $(Q)$(MAKE) KBUILD_SRC= ARCH=$(HEADER_ARCH) archheaders
> -
> +       $(Q)$(MAKE) -f $(srctree)/Makefile ARCH=$(HEADER_ARCH) archheaders
>
>  archprepare: include/generated/user_constants.h
>
> --
> 2.7.4
>
> --
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Kees Cook Sept. 15, 2018, 6:47 p.m. UTC | #2
On Fri, Aug 3, 2018 at 9:47 PM, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> Randy Dunlap reports UML occasionally fails to build with -j<N> and
> O=<builddir> options.

With v4.19-rc2 I'm still seeing a failure (for any parallelism) under ARCH=um

$ make -j8 ARCH=um O=/tmp/foo
...
/home/kees/src/linux-build/um/Makefile:1185: *** Headers not
exportable for the um architecture.  Stop.

Am I missing something?

-Kees
Masahiro Yamada Sept. 18, 2018, 4:01 a.m. UTC | #3
Hi Kees,


2018-09-16 3:47 GMT+09:00 Kees Cook <keescook@chromium.org>:
> On Fri, Aug 3, 2018 at 9:47 PM, Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
>> Randy Dunlap reports UML occasionally fails to build with -j<N> and
>> O=<builddir> options.
>
> With v4.19-rc2 I'm still seeing a failure (for any parallelism) under ARCH=um
>
> $ make -j8 ARCH=um O=/tmp/foo
> ...
> /home/kees/src/linux-build/um/Makefile:1185: *** Headers not
> exportable for the um architecture.  Stop.
>
> Am I missing something?


This is a different problem.

I sent a patch:
https://patchwork.kernel.org/patch/10603707/

Patch
diff mbox series

diff --git a/arch/um/Makefile b/arch/um/Makefile
index e54dda8..de340e4 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -122,8 +122,7 @@  archheaders:
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.asm-generic \
 	            kbuild-file=$(HOST_DIR)/include/uapi/asm/Kbuild \
 		    obj=$(HOST_DIR)/include/generated/uapi/asm
-	$(Q)$(MAKE) KBUILD_SRC= ARCH=$(HEADER_ARCH) archheaders
-
+	$(Q)$(MAKE) -f $(srctree)/Makefile ARCH=$(HEADER_ARCH) archheaders
 
 archprepare: include/generated/user_constants.h