linux-kernel - Re: [PATCH] x86: BUILD_IRQ say .text to avoid .data.percpu

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Message-ID: <20080724104459.GI28817@elte.hu>
Date:	Thu, 24 Jul 2008 12:44:59 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Mike Travis <travis@....com>, linux-kernel@...r.kernel.org,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH] x86: BUILD_IRQ say .text to avoid .data.percpu


* Hugh Dickins <hugh@...itas.com> wrote:

> When I edit the x86_64 Makefile to -fno-unit-at-a-time, bootup panics
> on 0xCCs in IRQ0x3e_interrupt(): IRQ0x20_interrupt etc. have got linked
> into .data.percpu.  Perhaps there are other ways of triggering that:
> specify ".text" in the BUILD_IRQ() macro for safety.
> 
> Signed-off-by: Hugh Dickins <hugh@...itas.com>

applied to tip/x86/urgent, thanks Hugh.

> I've been using -fno-unit-at-a-time (to lessen inlining, for easier 
> debugging) for a long time, but never saw this until Mike's percpu 
> mods came in: I mention this so you're on the lookout, just in case 
> other things are more likely to go into the wrong section now.  (I did 
> give Mike a private headsup on this a couple of weeks ago, in case it 
> helped with problems he was having with percpu, but in fact it didn't 
> help.)

Should we perhaps enable this automatically on CONFIG_FRAME_POINTER=y 
builds? Although a separate, default-off config option might be better, 
i'd not be surprised if there were more regressions in this area, it's a 
seldom used build vector.

	Ingo
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