linux-kernel - Re: [PATCH] x86: fully honor "nolapic" (take 2)

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Date:	Fri, 16 Jan 2009 14:58:51 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jan Beulich <jbeulich@...ell.com>
Cc:	tglx@...utronix.de, linux-kernel@...r.kernel.org, hpa@...or.com
Subject: Re: [PATCH] x86: fully honor "nolapic" (take 2)


* Jan Beulich <jbeulich@...ell.com> wrote:

> >>> Ingo Molnar <mingo@...e.hu> 16.01.09 14:42 >>>
> >
> >* Jan Beulich <jbeulich@...ell.com> wrote:
> >
> >> >>> Ingo Molnar <mingo@...e.hu> 16.01.09 13:45 >>>
> >> >
> >> >* Jan Beulich <jbeulich@...ell.com> wrote:
> >> >
> >> >> +	if (disable_apic) {
> >> >> +#ifdef CONFIG_X86_IO_APIC
> >> >> +		disable_ioapic_setup();
> >> >> +#endif
> >> >> +		return;
> >> >> +	}
> >> >
> >> > Shouldnt that #ifdef be avoided by always providing the function - 
> >> > just it is a NOP inline in the !CONFIG_X86_IO_APIC case?
> >> 
> >> That would make for a much bigger patch, since the io_apic.h doesn't 
> >> (and imo shouldn't) be included without that config option.
> >
> >But we are using io-apic functionality in that file, so we should include 
> >io_apic.h, right?
> 
> I don't generally (i.e. when !X86_IO_APIC) think so - anything accessing
> stuff from io_apic.c is guarded by a similar #ifdef.

and wrongly so - it proliferates ugly #ifdefs and sets us up for build 
failures like that. Developers cannot be expected to keep every build 
option in mind - we should provide an as homogenic and kconfig-invariant 
environment as possible.

	Ingo
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