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]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4AF18CD9.40201@redhat.com \
--to=riel@redhat.com \
--cc=Rajat.Jain@infogain.com \
--cc=bdonlan@gmail.com \
--cc=kernelnewbies@nl.linux.org \
--cc=linux-kernel@vger.kernel.org \
--cc=miloody@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox