linux-kernel - Re: kbuild: possible regression?

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Date:	Wed, 31 Oct 2007 10:43:06 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Jan Altenberg <jan.altenberg@...utronix.de>
Cc:	miltonm@....com, linux-kernel@...r.kernel.org,
	linux-kbuild <linux-kbuild@...r.kernel.org>
Subject: Re: kbuild: possible regression?

On Wed, Oct 31, 2007 at 10:03:50AM +0100, Jan Altenberg wrote:
> Hi all,
> 
> I'm not quite sure if this might be a regression, but I recognized a
> change to kbuild's behaviour, which causes some of my build scripts to
> fail.
> 
> The build scripts do:
> 
> return system(('make -C %s O=%s ARCH=%s CROSS_COMPILE=%s '+
>                       'oldconfig %s %s < /dev/null || exit %i') % 
>                       (srcdir, 
>                        builddir, 
>                        arch,
>                        crosscompile, 
>                        target,
>                        modules_target,
>                        FAILED_RETCODE))
> 
> which results in something like:
> 
> make -C /here/workdir/linux-2.6/common/src O=/here/workdir/linux-2.6/common/build/build \
> ARCH=i386 CROSS_COMPILE=/opt/i686-linux/bin/i686-linux- \
> oldconfig bzImage  < /dev/null || exit 1
> 
> In the past, oldconfig was the first target, which has been handled.
> 
> Now, bzImage seems to get handled at first. That causes my build scripts
> to fail, because the bzImage target does a silentoldconfig, which
> doesn't allow console redirection.
> 
> [...]
> 
> Kernel log buffer size (16 => 64KB, 17 => 128KB) (LOG_BUF_SHIFT) [14] 14
> Control Group support (CGROUPS) [N/y/?] (NEW) aborted!
> 
> Console input/output is redirected. Run 'make oldconfig' to update configuration.
> 
> make[5]: *** [silentoldconfig] Error 1
> make[4]: *** [silentoldconfig] Error 2
> make[3]: *** [include/config/auto.conf] Error 2
> make[2]: *** [sub-make] Error 2
> make[1]: *** [/here/workdir/linux-2.6/common/src/scripts/Kbuild.include] Error 2
> make: *** [sub-make] Error 2
> make: Leaving directory `/here/workdir/linux-2.6/common/src'
> 
> [...]
> 
> After silentoldconfig has failed, oldconfig seems to get executed and
> after that the bzImage build is starting. So far so good, BUT: My script
> checks the return value and fails after the execution of
> silentoldconfig. That's why I recognized the different behaviour.
> 
> I did a git bisect to identify the commit, which caused the change to
> kbuild's behaviour. The offending commit is:
> 
> commit 0b35786d77ba4037f181982cc8ca20a7a3bf0fd2
> Author: Milton Miller <miltonm@....com>
> Date:   Fri Sep 21 18:09:02 2007 -0500
> 
>     kbuild: call make once for all targets when O=.. is used
>     
>     Change the invocations of make in the output directory Makefile and the
>     main Makefile for separate object trees to pass all goals to one $(MAKE)
>     via a new phony target "sub-make" and the existing target _all.
>     
>     When compiling with separate object directories, a separate make is called
>     in the context of another directory (from the output directory the main
>     Makefile is called, the Makefile is then restarted with current directory
>     set to the object tree).  Before this patch, when multiple make command
>     goals are specified, each target results in a separate make invocation.
>     With make -j, these invocations may run in parallel, resulting in multiple
>     commands running in the same directory clobbering each others results.
>     
>     I did not try to address make -j for mixed dot-config and no-dot-config
>     targets.  Because the order does matter, a solution was not obvious.
>     Perhaps a simple check for MAKEFLAGS having -j and refusing to run would
>     be appropriate.
>     
>     Signed-off-by: Milton Miller <miltonm@....com>
>     Signed-off-by: Sam Ravnborg <sam@...nborg.org>
> 
> So, am I facing a kbuild regression?

Yes - I will try to fix it during the weekend (if Milton does not beat me).
Thanks for reporting and bisecting!

	Sam
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