linux-kernel - Re: [PATCH] "volatile considered harmful", take 3

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Message-ID: <46455394.6020302@zytor.com>
Date:	Fri, 11 May 2007 22:41:40 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Satyam Sharma <satyam.sharma@...il.com>
CC:	Jonathan Corbet <corbet@....net>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, Johannes Stezenbach <js@...uxtv.org>,
	Jesper Juhl <jesper.juhl@...il.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Heikki Orsila <shdl@...alwe.fi>,
	jimmy bahuleyan <knight.camelot@...il.com>,
	Stefan Richter <stefanr@...6.in-berlin.de>
Subject: Re: [PATCH] "volatile considered harmful", take 3

H. Peter Anvin wrote:
> 
> I don't see why Alan's way is necessarily better; it should work but is
> more heavy-handed as it's disabling *all* optimization such as loop
> invariants across the barrier.
> 

To expand on this further: the way this probably *should* be handled,
Linux-style, is with internally-volatile versions of le32_to_cpup() and
friends.  That obeys the concept that the volatility should be
associated with an operation, not a data structure, and, being related
to an I/O device, should have its endianness explicitly declared.

Right now those macros don't exist, however.

	-hpa
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