Commits
Masahiro Yamada committed 13d3d01e26b
um: fix parallel building with O= option
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.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Richard Weinberger <richard@nod.at>