linux-kernel - Re: [tip:x86/asm] x86, 64-bit: ifdef out struct thread

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Message-ID: <alpine.LFD.2.00.0905111323470.28914@localhost.localdomain>
Date:	Mon, 11 May 2009 13:25:00 -0400 (EDT)
From:	"Robert P. J. Day" <rpjday@...shcourse.ca>
To:	Alexey Dobriyan <adobriyan@...il.com>
cc:	Christoph Hellwig <hch@...radead.org>, mingo@...hat.com,
	hpa@...or.com, linux-kernel@...r.kernel.org, tglx@...utronix.de,
	mingo@...e.hu, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/asm] x86, 64-bit: ifdef out struct thread_struct::ip

On Mon, 11 May 2009, Alexey Dobriyan wrote:

> On Mon, May 11, 2009 at 8:03 PM, Christoph Hellwig <hch@...radead.org> wrote:
> > On Mon, May 11, 2009 at 03:09:40PM +0000, tip-bot for Alexey Dobriyan wrote:
> >> +#ifdef CONFIG_X86_32
> >>       unsigned long           ip;
> >> +#endif
> >>  #ifdef CONFIG_X86_64
> >>       unsigned long           fs;
> >>  #endif
> >
> > What happened to the good old concept of #if #else #endif?
>
> #else suggests alternative which is not the case.
> ->ip and ->fs can be in different parts of thread_struct.

  the arch/x86/Kconfig file certainly suggests that those are
mutually-exclusive alternatives:

...
# Select 32 or 64 bit
config 64BIT
        bool "64-bit kernel" if ARCH = "x86"
        default ARCH = "x86_64"
        ---help---
          Say yes to build a 64-bit kernel - formerly known as x86_64
          Say no to build a 32-bit kernel - formerly known as i386

config X86_32
        def_bool !64BIT

config X86_64
        def_bool 64BIT
...

unless there's something weird going on underneath.

rday
--

========================================================================
Robert P. J. Day                               Waterloo, Ontario, CANADA

        Linux Consulting, Training and Annoying Kernel Pedantry.

Web page:                                          http://crashcourse.ca
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