From: David Brownell <david-b@pacbell.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Jonathan Corbet <corbet@lwn.net>,
lkml <linux-kernel@vger.kernel.org>,
rtc-linux@googlegroups.com
Subject: Re: [PATCH] rtc: remove BKL for ioctl()
Date: Wed, 25 Jun 2008 16:04:49 -0700 [thread overview]
Message-ID: <200806251604.49995.david-b@pacbell.net> (raw)
In-Reply-To: <20080625233017.5b207e94@lxorguk.ukuu.org.uk>
On Wednesday 25 June 2008, Alan Cox wrote:
> >
> > Shouldn't that be -EINTR?
>
> For an ioctl case which should never be blocking for long periods it
> shouldn't be _interruptible in the first place, that will just introduce
> bizarre and weird bugs in application code.
>
> If there are slow ops they should drop and retake the lock.
What's a "long period"?
RTCs that connect using I2C or SPI will need to queue for access to
that particular serial bus, and then there are transfer costs.
The busses are frequently, but of course not always, idle. For I2C
at 100 KHz, RTC transfers might take a millisecond or so.
I'd be tempted to say those are all quick enough that the ops don't
need to be interruptible.
- Dave
next prev parent reply other threads:[~2008-06-25 23:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-23 2:55 [PATCH] rtc: remove BKL for ioctl() David Brownell
2008-06-25 8:57 ` [rtc-linux] " Alessandro Zummo
2008-06-25 22:39 ` Jonathan Corbet
2008-06-25 22:30 ` Alan Cox
2008-06-25 23:04 ` David Brownell [this message]
2008-06-25 23:41 ` Jonathan Corbet
2008-06-25 22:58 ` David Brownell
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=200806251604.49995.david-b@pacbell.net \
--to=david-b@pacbell.net \
--cc=alan@lxorguk.ukuu.org.uk \
--cc=corbet@lwn.net \
--cc=linux-kernel@vger.kernel.org \
--cc=rtc-linux@googlegroups.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.