linux-kernel - Re: [PATCH] mm: More _

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Date:	Mon, 18 Jun 2007 12:58:34 +0530
From:	"Satyam Sharma" <satyam.sharma@...il.com>
To:	"Yasunori Goto" <y-goto@...fujitsu.com>
Cc:	"Paul Mundt" <lethal@...ux-sh.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Sam Ravnborg" <sam@...nborg.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: More __meminit annotations.

On 6/18/07, Satyam Sharma <satyam.sharma@...il.com> wrote:
> Hi,
>
> On 6/18/07, Yasunori Goto <y-goto@...fujitsu.com> wrote:
> > > On Mon, Jun 18, 2007 at 02:49:24PM +0900, Yasunori Goto wrote:
> > > > > -static inline unsigned long zone_absent_pages_in_node(int nid,
> > > > > +static inline unsigned long __meminit zone_absent_pages_in_node(int nid,
> > > > >                                           unsigned long zone_type,
> > > > >                                           unsigned long *zholes_size)
> > > > >  {
> > > >
> > > > I thought __meminit is not effective for these static functions,
> > > > because they are inlined function. So, it depends on caller's
> > > > defenition. Is it wrong?
> > > >
> > > Ah, that's possible, I hadn't considered that. It seems to be a bit more
> > > obvious what the intention is if it's annotated, especially as this is
> > > the convention that's used by the rest of mm/page_alloc.c. A bit more
> > > consistent, if nothing more.
> >
> > I'm not sure which is intended. I found some functions define both
> > __init and inline in kernel tree. And probably, some functions don't
> > do it. So, it seems there is no convention.
> >
> > I'm Okay if you prefer both defined. :-)
>
> Marking inline functions as __init (or __meminit etc) is quite insane,
> IMHO. Note that all callers of the said inline function will also have to
> be __init anyway (else modpost will barf)

Actually, modpost will _not_ complain precisely _because_ kernel
uses always_inline so a separate body for the function will never be
emitted at all. But all callers of said inline function will *still* need to
be in __init anyway, else if the said inline function itself calls some
__init function (which is likely) and the caller of the said inline function
is not __init *then* modpost will complain.

> so the said function will
> have all callsites in .init.text anyway, and hence would be inlined
> in the same section as the caller (i.e. .init.text). [Note that kernel
> uses always_inline.]
>
> The annotation may still be a readability aid (which is subjective so
> one can't really comment upon), but asking gcc to put into a separate
> specified section, a function whose body would not be emitted by gcc
> separately at all, doesn't really make much sense syntactically _or_
> semantically -- gcc might not warn, of course, perhaps it's one of those
> little things it takes care of by itself silently without complaining (like
> taking pointers to inline functions).

All this is valid, still. Perhaps sparse warns / can be made to warn about
such cases (which may not be bugs, but weird C, at least)?
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