From: Rik van Riel <riel@redhat.com>
To: Bryan Donlan <bdonlan@gmail.com>
Cc: Rajat Jain <Rajat.Jain@infogain.com>, loody <miloody@gmail.com>,
linux-kernel@vger.kernel.org,
Kernel Newbies <kernelnewbies@nl.linux.org>
Subject: Re: why kernel implement "udelay" by cpu instructions?
Date: Wed, 04 Nov 2009 09:16:57 -0500 [thread overview]
Message-ID: <4AF18CD9.40201@redhat.com> (raw)
In-Reply-To: <3e8340490911032136x56696cc3u3b6f3b1e5d132324@mail.gmail.com>
On 11/04/2009 12:36 AM, Bryan Donlan wrote:
> I thought hrtimers allow higher-precision wakeups these days?
> Of course, if you only want to sleep for a few microseconds, the
> context switch might take longer than you want to sleep...
Also, you may not be in a context where you can schedule.
Sometimes drivers need to implement a small delay (to wait
for something on the device) while holding a spinlock or
while interrupts are disabled.
--
All rights reversed.
prev parent reply other threads:[~2009-11-04 14:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-02 3:13 why kernel implement "udelay" by cpu instructions? loody
2009-11-02 4:45 ` Rik van Riel
2009-11-04 2:19 ` loody
2009-11-04 5:01 ` Rajat Jain
2009-11-04 5:36 ` Bryan Donlan
2009-11-04 5:45 ` Rajat Jain
2009-11-04 14:16 ` Rik van Riel [this message]
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