linux-kernel - Re: [PATCH] CDROM: replace jiffies busyloop with msleep

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Date:	Wed, 23 May 2007 21:28:16 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Rene Herman <rene.herman@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Jeff Garzik <jeff@...zik.org>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH] CDROM: replace jiffies busyloop with msleep


* Rene Herman <rene.herman@...il.com> wrote:

> The trouble there is that unless you poll the bloody thing like mad 
> too much of the Q subchannels passes below you and you need a huge 
> number of retries to get anything out of it. I noticed when I started 
> adding audio bits that the driver took full seconds to complete some 
> audio requests while the old driver was snappy in that regard. When I 
> replaced our sleeping loop with a busy-wait same as the original the 
> snappyness returned and moreover, reading the TOC from the CD went 
> from something close to a minute to approximately a second. Thought 
> that minute was just because I was dealing with an old junk 1-speed 
> drive...

ouch ...

then i guess the right approach is to not use jiffies but to use a 
calculated number of udelay(10) calls or so.

	Ingo
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