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

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Message-ID: <20061202184821.GM3078@ftp.linux.org.uk>
Date:	Sat, 2 Dec 2006 18:48:21 +0000
From:	Al Viro <viro@....linux.org.uk>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	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 Sat, Dec 02, 2006 at 06:40:35PM +0000, Al Viro wrote:
> On Sat, Dec 02, 2006 at 07:27:56PM +0100, Thomas Gleixner wrote:
> > On Sat, 2006-12-02 at 18:19 +0000, Al Viro wrote:
> > > > This is going to make a lot of data structures smaller, when the
> > > > timer_list is embedded in the structure itself and for the lot, which
> > > > ignores the timer callback argument anyway.
> > > 
> > > container_of => still lousy type safety.  All over the sodding place.
> > 
> > Not less than timer->data, where timer data is void *
> 
> RTFPosting.  It might be void *, but it's set via SETUP_TIMER which
> does type checks before casting to void *.
> 
> IOW, I don't want _any_ typecasts/container_of necessary in the code.
> 
> Sane variant is
> 
> void foo_timer(struct net_device *dev)
> {
> 	...
> }
> 
> 	struct foo_dev *p = netdev_priv(dev);
> 	SETUP_TIMER(&p->timer, foo_timer, dev);
> 
> etc.
> 
> With warning generated if foo_timer(dev) would not be type safe.  Without
> typecasts.  Without container_of().  Without any bleeding cruft at all.

BTW, the same goes for tasklets and for work_struct.  Separate series,
obviously...
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