linux-kernel - Re: [RFC] timers, pointers to functions and type safety

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Date:	Sun, 3 Dec 2006 11:27:07 +0000
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Pavel Machek <pavel@....cz>
Cc:	Roman Zippel <zippel@...ux-m68k.org>,
	Al Viro <viro@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Matthew Wilcox <matthew@....cx>,
	Linus Torvalds <torvalds@...l.org>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] timers, pointers to functions and type safety

On Sun, Dec 03, 2006 at 11:21:09AM +0100, Pavel Machek wrote:
> Hi!
> 
> > > > The other alternative has real _practical_ value in almost every case, 
> > > > which I very much prefer. What's wrong with that?
> > > 
> > > Lack of any type safety whatsoever, magic boilerplates in callback instances,
> > > rules more complex than "your callback should take a pointer, don't cast
> > > anything, it's just a way to arrange for a delayed call, nothing magical
> > > needed"?
> > 
> > I admit the compile check in SETUP_TIMER() is clever, but this way all the
> > magic is in this place and is it really worth it? You're only adding _one_ 
> > extra typecheck for mostly simple cases anyway.
> 
> Well, there are so many of these simple changes, that SETUP_TIMER()
> with its clever trick looks very useful.

I agree with Al, Matthew and Pavel.  The current timer stuff is a pita
and needs fixing, and it seems Al has come up with a good way to do it
without adding additional crap into every single user of timers.

There *are* times when having the additional space for storing a pointer
is cheaper (in terms of number of bytes) than code to calculate an offset,
and those who have read the assembly code probably know this all too well.

Al - I look forward to your changes.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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