From: Jeff Garzik <jeff@garzik.org>
To: Bill Davidsen <davidsen@tmr.com>
Cc: Krzysztof Halasa <khc@pm.waw.pl>,
Robert Hancock <hancockr@shaw.ca>,
linux-kernel <linux-kernel@vger.kernel.org>,
Jonathan Corbet <corbet@lwn.net>
Subject: Re: [PATCH] "volatile considered harmful" document
Date: Sun, 13 May 2007 19:53:41 -0400 [thread overview]
Message-ID: <20070513235341.GA4270@havoc.gtf.org> (raw)
In-Reply-To: <46479E95.6050507@tmr.com>
On Sun, May 13, 2007 at 07:26:13PM -0400, Bill Davidsen wrote:
> Krzysztof Halasa wrote:
> >Robert Hancock <hancockr@shaw.ca> writes:
> >>You don't need volatile in that case, rmb() can be used.
> >rmb() invalidates all compiler assumptions, it can be much slower.
It does not invalidate /all/ assumptions.
> Yes, why would you use rmb() when a read of a volatile generates optimal
> code?
Read of a volatile is guaranteed to generate the least optimal code.
That's what volatile does, guarantee no optimization of that particular
access.
Jeff
next prev parent reply other threads:[~2007-05-13 23:53 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <fa.UIDGHS72acFv9jKylmdQQwWcXPA@ifi.uio.no>
[not found] ` <fa.fKNBJtZJWOQthlLjc1TDfY6jCLc@ifi.uio.no>
2007-05-12 18:32 ` Robert Hancock
2007-05-13 16:30 ` Krzysztof Halasa
2007-05-13 23:26 ` Bill Davidsen
2007-05-13 23:53 ` Jeff Garzik [this message]
2007-05-14 14:10 ` Bill Davidsen
2007-05-14 14:21 ` [2.6.21] circular locking dependency found in QUOTA OFF Folkert van Heusden
2007-05-14 17:43 ` Michal Piotrowski
2007-05-14 17:44 ` Folkert van Heusden
2007-05-15 14:09 ` Jan Kara
2007-05-15 17:52 ` Folkert van Heusden
2007-05-15 18:14 ` Jan Kara
2007-05-15 19:18 ` Jan Kara
2007-05-09 21:05 [PATCH] "volatile considered harmful" document Jonathan Corbet
2007-05-09 21:45 ` Jesper Juhl
2007-05-09 22:31 ` Satyam Sharma
2007-05-09 22:47 ` Jesper Juhl
2007-05-09 23:20 ` Satyam Sharma
2007-05-09 22:05 ` Heikki Orsila
2007-05-09 22:19 ` Randy Dunlap
2007-05-09 22:35 ` Scott Preece
2007-05-10 16:14 ` Giacomo A. Catenazzi
2007-05-10 19:35 ` H. Peter Anvin
2007-05-10 22:00 ` Alan Cox
2007-05-10 21:54 ` Bill Davidsen
2007-05-16 9:30 ` Thomas De Schampheleire
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