Subject: Re: user-mode port 0.44-2.4.7
To: cfriesen@nortelnetworks.com (Chris Friesen)
Date: Thu, 26 Jul 2001 00:49:26 +0100 (BST)
Cc: torvalds@transmeta.com (Linus Torvalds),
        linux-kernel@vger.kernel.org (linux-kernel)
In-Reply-To: <no.id> from "Chris Friesen" at Jul 25, 2001 07:37:20 PM
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Message-Id: <E15PYP8-0002uX-00@the-village.bc.nu>
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Original-Recipient: rfc822;linux-kernel-outgoing

> > This is not a gcc issue. Even if gcc _were_ to generate bad code, the
> > global volatile _still_ wouldn't be the correct answer.
> 
> I think his worry is the pedantic reason that without the volatile gcc is
> allowed to write code that chokes and dies if xtime happens to change in a
> volatile manner.  The example given earlier was:

Make the volatility explicit where it is needed, either to express a barrier
with barrier() or an assignment as in

	foo = (volatile)xtime

This makes it clear where the barriers are and avoids unpleasant
optimisation hits elsewhere.

Alan
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