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Date: Fri, 3 Apr 2009 01:56:46 +0200
From: Johannes Weiner <hannes@cmpxchg.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>, Sam Ravnborg <sam@ravnborg.org>,
       LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] kbuild: work around distcc/icecc madness
Message-ID: <20090402235646.GA9052@cmpxchg.org>
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On Fri, Mar 20, 2009 at 10:57:38PM +0100, Thomas Gleixner wrote:
> On Fri, 20 Mar 2009, Peter Zijlstra wrote:
> > > Changing from distcc to gcc will start a full rebuild on linus tree as
> > > well.
> > 
> > I just tried:
> > 
> > root@twins:/mnt/build/linux-2.6# /mnt/md0/cross/bin/x86_64-linux-gcc --version
> > x86_64-linux-gcc (GCC) 4.3.1 20080510 (prerelease)
> > Copyright (C) 2008 Free Software Foundation, Inc.
> > This is free software; see the source for copying conditions.  There is NO
> > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> > 
> > root@twins:/mnt/build/linux-2.6# gcc --version
> > gcc (Ubuntu 4.3.2-1ubuntu12) 4.3.2
> > Copyright (C) 2008 Free Software Foundation, Inc.
> > This is free software; see the source for copying conditions.  There is NO
> > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> > 
> > The build with the distcc x86_64-linux-gcc compiler and the install
> > using the host compiler works just fine on Linus' tree.
> 
> Hmm, I went through all the Makefile changes and we do not touch those
> bits at all.
> 
> Can you check whether builddir/scripts/mod/.empty.o.cmd has
> -DCONFIG_AS_CFI in the command line ?
> 
> Can you check that file after you built -tip (w/o my patch) and after
> your make install started to rebuild the tree ?

Perhaps 'make V=2 install' can also help figuring out why the targets
are rebuilt?

HTH, Hannes