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Date: Thu, 29 Jan 2009 14:27:34 -0500
From: Neil Horman <nhorman@tuxdriver.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Simon Horman <horms@verge.net.au>, Randy Dunlap <randy.dunlap@oracle.com>,
       linux-kernel@vger.kernel.org, Miao Xie <miaox@cn.fujitsu.com>,
       Vivek Goyal <vgoyal@redhat.com>
Subject: Re: mmotm 2009-01-28-02-17 uploaded (i386 build errors: cpusets &
	kexec)
Message-ID: <20090129192734.GA10037@hmsreliant.think-freely.org>
References: <200901281019.n0SAJ9C6013727@imap1.linux-foundation.org> <49808E3F.1090805@oracle.com> <20090128163040.88b05b3d.akpm@linux-foundation.org> <20090129022846.GA1319@verge.net.au> <20090129120935.GB9221@hmsreliant.think-freely.org> <20090129100157.965bd396.akpm@linux-foundation.org>
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On Thu, Jan 29, 2009 at 10:01:57AM -0800, Andrew Morton wrote:
> On Thu, 29 Jan 2009 07:09:35 -0500 Neil Horman <nhorman@tuxdriver.com> wrote:
> 
> > > > So does that.
> > > > 
> > > > --- a/kernel/printk.c~kexec-add-dmesg-log-symbols-to-proc-vmcoreinfo-lists-fix-fix
> > > > +++ a/kernel/printk.c
> > > > @@ -137,11 +137,13 @@ static char *log_buf = __log_buf;
> > > >  static int log_buf_len = __LOG_BUF_LEN;
> > > >  static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
> > > >  
> > > > +#ifdef CONFIG_KEXEC
> > > >  void log_buf_kexec_setup(void)
> > > >  {
> > > >  	VMCOREINFO_SYMBOL(log_buf);
> > > >  	VMCOREINFO_SYMBOL(log_end);
> > > >  }
> > > > +#endif
> > > >  
> > > >  static int __init log_buf_len_setup(char *str)
> > > >  {
> > > > _
> > > 
> > > Weird, I thought I checked that just now. In any case this email
> > > was already in my inbox. In any case, I can now produce the problem,
> > > and this patch resolves it.
> > > 
> > 
> > Sorry, i didn't think to check on conditions when CONFIG_KEXEC wasn't set.  I
> > assumed we had a stub for all the VMCOREINFO defines.  Why don't we fix it in
> > that manner?  I mean we have serveral arch specific additions to vmcoreinfo, all
> > of which apparently must be ifdefd for this to work.  Why not just fix it in
> > conditional definition?
> 
> I didn't do that because then we'd have an empty function log_buf_kexec_setup()
> floating about in every vmlinux.
> 
> Hardly a big issue, but a bit regrettable.
> 
Won't the compiler just eliminate that symbol during final link, given that its
not an exported symbol?
Neil