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Message-ID: <4AAEBABA.9060108@gmail.com>
Date: Mon, 14 Sep 2009 23:50:50 +0200
From: Jiri Slaby <jirislaby@gmail.com>
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To: Andreas Mohr <andi@lisas.de>
CC: Guennadi Liakhovetski <g.liakhovetski@gmx.de>,
       Mauro Carvalho Chehab <mchehab@infradead.org>,
       Luca Risolia <luca.risolia@studio.unibo.it>,
       linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: V4L2 drivers: potentially dangerous and inefficient msecs_to_jiffies()
 calculation
References: <20090914210741.GA16799@rhlx01.hs-esslingen.de> <4AAEB6F0.4080706@gmail.com> <20090914213933.GA5468@rhlx01.hs-esslingen.de>
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On 09/14/2009 11:39 PM, Andreas Mohr wrote:
> On Mon, Sep 14, 2009 at 11:34:40PM +0200, Jiri Slaby wrote:
>> On 09/14/2009 11:07 PM, Andreas Mohr wrote:
>>> msecs_to_jiffies(1) is quite a bit too boldly assuming
>>> that all of the msecs_to_jiffies(x) implementation branches
>>> always round up.
>>
>> They do, don't they?
> 
> I'd hope so, but a slight risk remains, you never know,
> especially with 4+ or so variants...

A potential problem here is rather that it may wait longer due to
returning 1 jiffie. It's then timeout * 1000 * 1. On 250HZ system it
makes a difference of multiple of 4. Don't think it's a real issue in
those drivers at all, but it's worth fixing. Care to post a patch?