linux-kernel - Re: nfs: __setup_str_nfs_root_setup causes a section type conflict

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Date:	Mon, 03 Aug 2009 18:11:33 -0400
From:	Trond Myklebust <trond.myklebust@....uio.no>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	Frans Pop <elendil@...net.nl>, linux-kernel@...r.kernel.org,
	linux-nfs@...r.kernel.org, parisc-linux@...ts.parisc-linux.org,
	Helge Deller <deller@....de>
Subject: Re: nfs: __setup_str_nfs_root_setup causes a section type conflict

On Mon, 2009-08-03 at 23:52 +0200, Sam Ravnborg wrote:
> On Mon, Aug 03, 2009 at 05:07:23PM -0400, Trond Myklebust wrote:
> > On Mon, 2009-08-03 at 22:57 +0200, Frans Pop wrote:
> > > $ make init/do_mounts.o
> > >   CHK     include/linux/version.h
> > >   CHK     include/linux/utsrelease.h
> > >   SYMLINK include/asm -> include/asm-parisc
> > >   CALL    scripts/checksyscalls.sh
> > >   CC      init/do_mounts.o
> > > 
> > > while:
> > > 
> > > $ make fs/nfs/nfsroot.o
> > >   CHK     include/linux/version.h
> > >   CHK     include/linux/utsrelease.h
> > >   SYMLINK include/asm -> include/asm-parisc
> > >   CALL    scripts/checksyscalls.sh
> > >   CC      fs/nfs/nfsroot.o
> > > fs/nfs/nfsroot.c:403: error: __setup_str_nfs_root_setup causes a section type 
> > > conflict
> > 
> > To me that looks like some kind of compiler bug.
> 
> unspecified behaviour is a better name for it.
> 
> We have two variables we have forced a section on.
> One variable is marked RO by the compiler while the other is not.
> This results in a section type conflict because all
> symbols needs to have the same falgs.
> 
> We usually triggers this with powerpc builds (64 bit IIRC),
> and now with parisc too.
> 
> The only way to fix it is to move one of the offending
> variables to __initdata.
> There is two variales to consider - the compiler only
> mention one of them.
> 
> Trying to declare the variables const etc usually has
> no good effect.

So why would it be happening in the NFSroot case, but not in
do_mounts.c? They're both using the standard __setup() macro with a
constant string, and an __init function argument.

Futhermore, when grepping for '__initconst', it seems that the
combination with 'static const' is the norm rather than the exception.

Trond

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