linux-kernel - Re: [PATCH] x86: fix improper .init-type section references

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Message-ID: <20070612175606.GB15329@uranus.ravnborg.org>
Date:	Tue, 12 Jun 2007 19:56:06 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Jan Beulich <jbeulich@...ell.com>
Cc:	Satyam Sharma <satyam.sharma@...il.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Andi Kleen <ak@...e.de>, linux-kernel@...r.kernel.org,
	patches@...-64.org
Subject: Re: [PATCH] x86: fix improper .init-type section references

On Tue, Jun 12, 2007 at 02:43:55PM +0200, Jan Beulich wrote:
> >> The cacheinfo_cpu_notifier itself is called out from _cpu_down() which
> >> is ... yep, *not* __cpuinit (and obviously *cannot* be so). _cpu_down()
> >> is called from cpu_down() which is (thankfully!) protected inside
> >> #ifdef CONFIG_HOTPLUG_CPU, so we've /just about/ escaped trouble
> >> so far, but another of it's callers is disable_nonboot_cpus() which does
> >> *not* depend on HOTPLUG_CPU, but is #ifdef'ed inside SUSPEND_SMP
> >> (gargh!) instead, and ... is _not_ __cpuinit either (obviously, again).
> >
> >Wait, SUSPEND_SMP again depends on HOTPLUG_CPU, so there
> >are no issues here in marking cache_remove_dev() __cpuexit
> >(which effectively simply becomes #ifdef HOTPLUG_CPU) as all
> >callsites that call out the notifier with CPU_DEAD/FROZEN are also
> >going to be disabled. [ Ok, looks like using __cpuexit as this kind of
> >pseudo-#ifdef HOTPLUG_CPU is a standard practice? ]
> >
> >But modpost will still complain (bogus warning) about calling __exit
> >from __init (when HOTPLUG_CPU=n) for cacheinfo_cpu_callback()
> >calling cache_remove_dev(), no?
> 
> No, it doesn't, at least not for me. And from a purely theoretical
> perspective I don't think such references should be considered bad -
> .exit.* should be discarded together with .init.* if unloading is
> impossible (built-in or configured off), not before module/kernel
> initialization. This is specifically because init code may want to utilize
> exit code in case of initialization failure.

For the builtin case some arch's drop exit code during link time
so using function marked __exit from __init will cause a
linker bug. For i386 __exit is discarded at runtime - but dunno when in the
init sequence.

	Sam
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