Masahiro Yamada d2f8ae0e4c kbuild: turn auto.conf.cmd into a mandatory include file
syncconfig is responsible for keeping auto.conf up-to-date, so if it
fails for any reason, the build must be terminated immediately.

However, since commit 9390dff66a ("kbuild: invoke syncconfig if
include/config/auto.conf.cmd is missing"), Kbuild continues running
even after syncconfig fails.

You can confirm this by intentionally making syncconfig error out:

  diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
  index 08ba146..307b9de 100644
  --- a/scripts/kconfig/confdata.c
  +++ b/scripts/kconfig/confdata.c
  @@ -1023,6 +1023,9 @@ int conf_write_autoconf(int overwrite)
          FILE *out, *tristate, *out_h;
          int i;

  +       if (overwrite)
  +               return 1;
  +
          if (!overwrite && is_present(autoconf_name))
                  return 0;

Then, syncconfig fails, but Make would not stop:

  $ make -s mrproper allyesconfig defconfig
  $ make
  scripts/kconfig/conf  --syncconfig Kconfig

  *** Error during sync of the configuration.

  make[2]: *** [scripts/kconfig/Makefile;69: syncconfig] Error 1
  make[1]: *** [Makefile;557: syncconfig] Error 2
  make: *** [include/config/auto.conf.cmd] Deleting file 'include/config/tristate.conf'
  make: Failed to remake makefile 'include/config/auto.conf'.
    SYSTBL  arch/x86/include/generated/asm/syscalls_32.h
    SYSHDR  arch/x86/include/generated/asm/unistd_32_ia32.h
    SYSHDR  arch/x86/include/generated/asm/unistd_64_x32.h
    SYSTBL  arch/x86/include/generated/asm/syscalls_64.h
  [ continue running ... ]

The reason is in the behavior of a pattern rule with multi-targets.

  %/auto.conf %/auto.conf.cmd %/tristate.conf: $(KCONFIG_CONFIG)
          $(Q)$(MAKE) -f $(srctree)/Makefile syncconfig

GNU Make knows this rule is responsible for making all the three files
simultaneously. As far as examined, auto.conf.cmd is the target in
question when this rule is invoked. It is probably because auto.conf.cmd
is included below the inclusion of auto.conf.

The inclusion of auto.conf is mandatory, while that of auto.conf.cmd
is optional. GNU Make does not care about the failure in the process
of updating optional include files.

I filed this issue (https://savannah.gnu.org/bugs/?56301) in case this
behavior could be improved somehow in future releases of GNU Make.
Anyway, it is quite easy to fix our Makefile.

Given that auto.conf is already a mandatory include file, there is no
reason to stick auto.conf.cmd optional. Make it mandatory as well.

Cc: linux-stable <stable@vger.kernel.org> # 5.0+
Fixes: 9390dff66a ("kbuild: invoke syncconfig if include/config/auto.conf.cmd is missing")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-05-18 11:49:54 +09:00
2019-05-16 15:51:55 -07:00
2019-05-16 15:51:55 -07:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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