linux-kernel - Re: [PATCH] kbuild: Run syncconfig with -s

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Date:   Mon, 14 Sep 2020 14:37:08 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>
Subject: Re: [PATCH] kbuild: Run syncconfig with -s


* Masahiro Yamada <masahiroy@...nel.org> wrote:

> On Thu, Aug 20, 2020 at 3:35 PM Ingo Molnar <mingo@...nel.org> wrote:
> >
> > On every kernel build that runs --syncconfig, there's an output of the following line:
> >
> >   scripts/kconfig/conf  --syncconfig Kconfig
> >
> > This is the only non-platform build message the kbuild system emits that isn't
> > prefixed by at least a space, or is a build warning.
> >
> > Run it under -s - if there's any problem it will emit messages anyway.
> >
> > With this change the following simple grep filter will show all build warnings
> > and errors of a kernel build:
> >
> >    make | grep -v '^ '
> 
> 
> 
> I do want to see something when syncconfig is invoked.
> 
> I will apply this instead:
> https://patchwork.kernel.org/patch/11727445/

BTW., there's another, rather spurious bug I recently triggered in kbuild.

Occasionally when I Ctrl-C a kernel build on a system with a lot of CPUs, 
the .o.cmd file gets corrupted:

  mm/.pgtable-generic.o.cmd:5: *** unterminated call to function 'wildcard': missing ')'.  Stop.
  make: *** [Makefile:1788: mm] Error 2
  make: *** Waiting for unfinished jobs....

The .o.cmd file is half-finished:

    $(wildcard include/config/shmem.h) \
    $(wildcard include/config/hugetlb/page.h) \
    $(wildcard include/config/zone/device.h) \
    $(wildcard include/config/dev/pagemap/ops.h) \
    $(wildcard include/config/device/private.h) \
    $(wildcard include/config/pci/p2pdma.h) \
    $(wildcard include/config/sparsemem.h) \
    $(wildcard include/config/sparsemem/vmemmap.h) \
    $(wildcard include/config/numa/balancing.h) \
    $(wildcard i
    [premature EOF]

Instead of the regular rules that end in:

    $(wildcard include/config/memory/hotplug/sparse.h) \

    mm/pgtable-generic.o: $(deps_mm/pgtable-generic.o)

    $(deps_mm/pgtable-generic.o):
    [regular EOF]

Manually removing the corrupted .o.cmd dot file solves the bug.

There's no reproducer other than Ctrl-C-ing large build jobs a couple of times.

Thanks,

	Ingo