linux-kernel - Re: V4L2 drivers: potentially dangerous and inefficient msecs_to

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Message-ID: <20090919100809.GA22683@rhlx01.hs-esslingen.de>
Date:	Sat, 19 Sep 2009 12:08:09 +0200
From:	Andreas Mohr <andi@...as.de>
To:	Andreas Mohr <andi@...as.de>
Cc:	Marcin Slusarz <marcin.slusarz@...il.com>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Luca Risolia <luca.risolia@...dio.unibo.it>,
	linux-media@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	jirislaby@...il.com
Subject: Re: V4L2 drivers: potentially dangerous and inefficient
	msecs_to_jiffies() calculation

Hi,

On Tue, Sep 15, 2009 at 09:21:46PM +0200, Andreas Mohr wrote:
> Hi,
> 
> On Tue, Sep 15, 2009 at 09:14:19PM +0200, Marcin Slusarz wrote:
> > Or better: frame_timeout * HZ
> 
> D'oh! ;-)
> 
> But then what about the other 3 bazillion places in the kernel
> doing multiples of seconds?
> 
> linux-2.6.31]$ find . -name "*.c"|xargs grep msecs_to_jiffies|grep 1000|wc -l
> 73
> 
> If this expression is really better (also/especially from a maintenance POV),
> then it should get changed.

I just saw that my unmodified patch has been committed.
I think that that is ok or even preferrable, since "HZ" is a lot
less greppable (you'd have to use "\<HZ\>") or uniform than msecs_to_jiffies.
In terms of "number of traps avoided" the expressions should be equivalent.

Thanks!

Andreas Mohr
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