linux-kernel - Re: Introduce down

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Message-ID: <20080418225508.GF20637@parisc-linux.org>
Date:	Fri, 18 Apr 2008 16:55:09 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Introduce down_killable()

On Fri, Apr 18, 2008 at 03:34:55PM -0700, Andrew Morton wrote:
> On Fri, 18 Apr 2008 17:05:06 GMT
> Linux Kernel Mailing List <linux-kernel@...r.kernel.org> wrote:
> 
> > --- a/kernel/semaphore.c
> > +++ b/kernel/semaphore.c
> > @@ -34,6 +34,7 @@
> >  
> >  static noinline void __down(struct semaphore *sem);
> >  static noinline int __down_interruptible(struct semaphore *sem);
> > +static noinline int __down_killable(struct semaphore *sem);
> >  static noinline void __up(struct semaphore *sem);
> 
> What is the reason for all the noinlines in this file?

Copied from kernel/mutex.c ;-)

The reason is to make sure that __down_interruptible (et al) are
out-of-line from down_interruptible, and that __down_common is inlined
into __down_interruptible().

> Something to do with getting proper wchan output?  I guess it doesn't hurt
> from a documentation POV, but did you find that it was actually necessary?
> 
> IOW: is gcc now capable of secretly inlining functions which are defined
> further ahead in the compilation unit?

With -funit-at-a-time, I believe it is capable of that.

> (did you actually "test" the wchan stuff, btw?)

I tested that wchan still produces the right output, yes.

-- 
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"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
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