linux-kernel - Re: [PATCH 3/3] x86/irq: update first_system_vector only when X86_LOCAL

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Date:	Sun, 13 Mar 2016 12:12:11 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jianyu Zhan <nasa4836@...il.com>
cc:	mingo@...hat.com, "H. Peter Anvin" <hpa@...or.com>,
	Aravind.Gopalakrishnan@....com, brgerst@...il.com, bp@...e.de,
	feng.wu@...el.com, jiang.liu@...ux.intel.com,
	Tejun Heo <tj@...nel.org>, dvlasenk@...hat.com,
	penberg@...helsinki.fi, Yinghai Lu <yhlu.kernel@...il.com>,
	andi@...stfloor.org, Andy Lutomirski <luto@...nel.org>,
	ajm@....com, Yinghai Lu <yinghai@...nel.org>,
	Akinobu Mita <akinobu.mita@...il.com>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] x86/irq: update first_system_vector only when
 X86_LOCAL_PIC is on

On Sun, 13 Mar 2016, Jianyu Zhan wrote:
> On Sun, Mar 13, 2016 at 5:33 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> >       IRQ_WORK can work w/o APIC
> >
> > Emphasis on CAN. If the APIC is available it's used, if not then there is no
> > point in setting up the gate for nothing.
> >
> > So why would your patch do any good?
> 
> I understood it is no point setting up if  APIC is not available,  but
> just got confused by
> your wording 'can',  now all clear.
> 
> As for the patch set.   My initial purpose is just wanting to make the
> layout clear and
> clean up stale comments and dead code:
> 
> #ifndef CONFIG_X86_LOCAL_APIC
> #define first_system_vector NR_VECTORS
> #endif
> 
> as we've talked about this before,  it won't ever be change on
> !CONFIG_X86_LOCAL_APIC,
> so no point define it here(it is initialized to NR_VECTORS).

Hell no. If CONFIG_X86_LOCAL_APIC=n then first_system_vector is not a variable
and not available and not initialized at all.

> Since all points are clear now, 

Obviously not.