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

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Message-ID: <a781481a0706120421l94f8d8dk864f288d63c01b1a@mail.gmail.com>
Date:	Tue, 12 Jun 2007 16:51:04 +0530
From:	"Satyam Sharma" <satyam.sharma@...il.com>
To:	"Jan Beulich" <jbeulich@...ell.com>
Cc:	"Sam Ravnborg" <sam@...nborg.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix improper .init-type section references

On 6/12/07, Jan Beulich <jbeulich@...ell.com> wrote:
> >> -static __init void kthreadd_setup(void)
> >> +static noinline __init_refok void kthreadd_setup(void)
> >>  {
> >>         struct task_struct *tsk = current;
> >
> >This isn't ok. There isn't any __init function that is (safely) referenced
> >by kthreadd_setup(), so we shouldn't really be marking it as such.
> >Also, kthreadd_setup() is really only ever called at init time, so we'd
> >want it to remain __init.
>
> Oh, I see, I misunderstood the purpose of the tag - I assumed it would
> mark an __init function that is known to only be referenced from init-only
> code paths inside non-init functions (i.e. I didn't pay attention that the
> resulting section's name is .text.init.refok, not .init.text.refok).
>
> I have to admit I have some difficulty understanding when the tags
> are going to be useful the way they are implemented right now.

Yup, I had discussed precisely the same issue (whether to associate
__init_refok with callers or callees) with Sam earlier, but he thought
it'd be more useful to have normal-caller-can-ref-init-callees semantics
for the same.

> >I believe the correct fix to silence modpost here would be to mark its
> >caller kthreadd() also as __init, because it too is used only at init time?
>
> I don't think so - it is my understanding that this is the body of a thread
> that never dies.

Ugh, yes, I'm smoking God-knows-what, and you're absolutely correct!

So we should be marking kthreadd() as __init_refok instead, it seems.

Satyam
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