linux-kernel - Re: [PATCH/RFC] msleep() with hrtimers

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Date:	Tue, 17 Jul 2007 14:04:56 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Nish Aravamudan <nish.aravamudan@...il.com>
CC:	Ray Lee <ray-lk@...rabbit.org>,
	Roman Zippel <zippel@...ux-m68k.org>,
	Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH/RFC] msleep() with hrtimers

Nish Aravamudan wrote:

> Well, before these changes, the only guarantee msleep() could make,
> just like the only guarantee schedule_timeout() could make, was that
> it would not return early. The 1-jiffy sleep was always tough to deal
> with, because of rounding and such. And it's simply exacerbated with
> HZ=100. It's not technically 20 times longer in all cases, it's 2
> jiffies longer, which depends on HZ, so varies from 2 msecs longer to
> 20 msecs longer.

I don't think you should rely on anything else actually, because Linux
is not an RT OS. If your driver needs a specific sequence in a given
amount of time, you have to do something like disable interrupts and
use delays.

-- 
SUSE Labs, Novell Inc.
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