linux-kernel - Re: [PATCH 3/3] Makes lguest's irq handler typesafe

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Message-Id: <200801191228.30363.rusty@rustcorp.com.au>
Date:	Sat, 19 Jan 2008 12:28:29 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Tejun Heo <htejun@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jeff Garzik <jgarzik@...ox.com>,
	Ash Willis <ashwillis@...grammer.net>,
	linux-pcmcia@...ts.infradead.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 3/3] Makes lguest's irq handler typesafe

On Saturday 19 January 2008 10:12:33 Tejun Heo wrote:
> Type safety is good but I doubt this would be worth the complexity.  It
> has some benefits but there's much larger benefit in keeping things in
> straight C.  People know that functions take fixed types and are also
> familiar with the convention of passing void * for callback arguments.
> IMHO, staying in line with those common knowledges easily trumps having
> type checking on interrupt handler.

I sympathise with this argument, but I think just because people are familiar 
with existing hacks shouldn't prevent improvement.  I think the resulting 
code is clearer and more readable.

Even in the implementation, the tricky part is the check_either_type() macro: 
the rest is straight-forward.

> Also, how often do we see a bug where things go wrong because interrupt
> handler is given the wrong type of argument?  Even when such bug
> happens, I doubt it can escape the developer's workstation if he/she is
> paying any attention to testing.

I agree this one is unlikely.  But I am trying to spread type-safety more 
widely (see previous kthread patches).

I like changing the kernel to make life simpler for developers.  We don't do 
enough of it.

Cheers,
Rusty.
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