linux-kernel - Re: [PATCH x86] [15/16] Force __cpuinit on for CONFIG_PM without HOTPLUG

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Date:	Tue, 15 Jan 2008 19:21:42 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Adrian Bunk <bunk@...nel.org>,
	rjw@...k.pl, pavel@...e.cz, linux-kernel@...r.kernel.org
Subject: Re: [PATCH x86] [15/16] Force __cpuinit on for CONFIG_PM without HOTPLUG_CPU

> > 
> > The plan is to let section mismatch warnings become errors 
> > after the merge window - so we hit -mm first.
> 
> A lot of those I look at seem to be not really bugs; also my
> impression is that they sometimes crop up randomly. e.g. you
> change something completely unrelated and suddenly you get
> a section warning somewhere else.
I have fixed a lot of these warnings.
And when I look closer at them they are explainable.

The warnings are today very dependent on the configuration
and the inlining that gcc uses.
With default options to gcc my .config produces ~65 warnings
but with -fno-unit-a-time I get 112 warnings.
Solely due to less inlining done by gcc.

So there are two sources for the 'randomization':
a) The actual config
b) The sometimes agressive inlining

a) will be addressed by having separate sections for each
__init* type that is at link time combined where it belongs.

b) is addressed by a Kernel Hacking option which
   1) uses -fno-unit-at-a-time to get less gcc inlining
   2) maybe make all __*init function no-inline
   3) maybe disable inlining globally

> > And I will add a config option to:
> > - set -fno-unit-at-a-time
> 
> I was told future gcc versions would remove that. Why do you
> want it?
Are there any better way to tell gcc no to inline so agressively?

	Sam
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