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From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: linux-kbuild@vger.kernel.org
Cc: Jeff Dike <jdike@addtoit.com>,
	Richard Weinberger <richard@nod.at>,
	linux-um@lists.infradead.org,
	Randy Dunlap <rdunlap@infradead.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Michal Marek <michal.lkml@markovi.net>,
	Sam Ravnborg <sam@ravnborg.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH 1/3] um: fix parallel building with O= option
Date: Sat,  4 Aug 2018 13:47:01 +0900	[thread overview]
Message-ID: <1533358023-5801-2-git-send-email-yamada.masahiro@socionext.com> (raw)
In-Reply-To: <1533358023-5801-1-git-send-email-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.

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


  reply	other threads:[~2018-08-04  4:49 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-04  4:47 [PATCH 0/3] Kbuild: fix and clean-up arch/um/Makefile Masahiro Yamada
2018-08-04  4:47 ` Masahiro Yamada [this message]
2018-08-04  4:51   ` [PATCH 1/3] um: fix parallel building with O= option Masahiro Yamada
2018-09-15 18:47   ` Kees Cook
2018-09-18  4:01     ` Masahiro Yamada
2018-08-04  4:47 ` [PATCH 2/3] kbuild: add %asm-generic to no-dot-config-targets Masahiro Yamada
2018-08-04  4:47 ` [PATCH 3/3] um: clean up archheaders recipe Masahiro Yamada
2018-08-05  0:58 ` [PATCH 0/3] Kbuild: fix and clean-up arch/um/Makefile Randy Dunlap
2018-08-06 20:54 ` Richard Weinberger
2018-08-08  1:24   ` Masahiro Yamada

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