linux-kernel - Re: dealing with excessive includes

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Message-ID: <20061023013604.GF25210@parisc-linux.org>
Date:	Sun, 22 Oct 2006 19:36:04 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Andi Kleen <ak@...e.de>
Cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Randy Dunlap <rdunlap@...otime.net>,
	Stefan Richter <stefanr@...6.in-berlin.de>,
	Al Viro <viro@....linux.org.uk>,
	Linus Torvalds <torvalds@...l.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	linux-arch@...r.kernel.org
Subject: Re: dealing with excessive includes

On Mon, Oct 23, 2006 at 03:31:16AM +0200, Andi Kleen wrote:
> On Monday 23 October 2006 03:08, Matthew Wilcox wrote:
> > On Mon, Oct 23, 2006 at 02:42:58AM +0200, Andi Kleen wrote:
> > > 
> > > > /*+
> > > >  * Provides: struct sched
> > > >  * Provides: total_forks, nr_threads, process_counts, nr_processes()
> > > >  * Provides: nr_running(), nr_uninterruptible(), nr_active(), nr_iowait(), weighted_cpuload()
> > > >  */
> > > 
> > > That's ugly.  If it needs that i don't think it's a good idea.
> > > We really want standard C, not some Linux dialect.
> > 
> > Um, that's a comment.  It's standard C.
> 
> If you require it to do something it isn't a comment anymore -- it would become
> a language extension.

How is this any different from __iomem annotations?

> > Here's the problem.  If a file needs canonicalize_irq(), it should
> > include <linux/interrupt.h> (which eventually ends up including
> > asm/irq,h), and not <asm/irq.h> (where it's defined).
> > If a file needs add_wait_queue(), it should include <linux/wait.h>
> > (where it's defined) and not <linux/fs.h> (which directly includes
> > linux/wait.h>.
> > 
> > Please define an algorithm which distinguishes the two cases.
> 
> Needs are inside {} or in a macro definition
> So if the identifier happens after #define or inside {} assume the symbol
> is needed from somewhere else, otherwise it is declared here.
> 
> That is likely not 100% foolproof, but should be good enough and
> the mismatches can be resolved by hand.

Let me try to explain the problem again, because what you wrote has
nothing to do with the problem.

canonicalize_irq() is defined in <asm/irq.h>.  No .c file should be
including <asm/irq.h> in order to get it.  It should be including
<linux/interrupt.h>, which will indirectly pull in <asm/irq.h>

add_wait_queue() is defined in <linux/wait.h>.  .c files wishing to use
add_wait_queue() should be including <linux/wait.h> rather than relying
on it being pulled in through some other path.

This needs annotations to fix, or a big bag of unreliable heuristics.
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