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Date: Thu, 25 Nov 2010 07:30:29 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Valdis.Kletnieks@vt.edu
Cc: Jesper Juhl <jj@chaosbits.net>, Rakib Mullick <rakib.mullick@gmail.com>,
        Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
        x86@kernel.org
Subject: Re: [PATCH] x86, dumpstack: Fix unused variable warning.
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Le Wed, 24 Nov 2010 23:07:47 -0500,
Valdis.Kletnieks@vt.edu a écrit :

> On Wed, 24 Nov 2010 10:57:10 +0100, Jesper Juhl said:
> 
> > On Wed, 24 Nov 2010, Rakib Mullick wrote:
> 
> > > diff --git a/arch/x86/kernel/dumpstack.c
> > > b/arch/x86/kernel/dumpstack.c index 8474c99..fc5a253 100644
> > > --- a/arch/x86/kernel/dumpstack.c
> > > +++ b/arch/x86/kernel/dumpstack.c
> > > @@ -197,10 +197,10 @@ void show_stack(struct task_struct *task,
> > > unsigned long *sp)
> > >   */
> > >  void dump_stack(void)
> > >  {
> > > -	unsigned long bp = 0;
> > >  	unsigned long stack;
> > > 
> > >  #ifdef CONFIG_FRAME_POINTER
> > > +	unsigned long bp = 0;
> > >  	if (!bp)
> > >  		get_bp(bp);
> > >  #endif
> > 
> > So, now the bp variable does not exist at all if
> > CONFIG_FRAME_POINTER is not defined.
> > That's going to make this line :
> > 
> >           show_trace(NULL, NULL, &stack, bp);
> > 
> > found further down in the dump_stack() function, quite unhappy.
> 
> OK, I'll bite.  Why does the original say 'unsigned long bp = 0;' and
> then turns around and has an 'if (!bp)' check?  Why is the
> conditional there?

The original check was indeed not necessary. But now the whole block
should be removed anyway.