linux-kernel - Re: [PATCH] x86: Remove readq()/writeq() on 32-bit

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Message-ID: <4A0B3605.8090007@zytor.com>
Date:	Wed, 13 May 2009 14:05:09 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeff Garzik <jeff@...zik.org>
CC:	Hitoshi Mitake <h.mitake@...il.com>,
	Roland Dreier <rdreier@...co.com>, Ingo Molnar <mingo@...e.hu>,
	David Miller <davem@...emloft.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	tglx@...utronix.de, rpjday@...shcourse.ca,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Remove readq()/writeq() on 32-bit

Jeff Garzik wrote:
> 
> Roland's patch was acked, apparently, _in spite of_ the commonly 
> accepted readq() definition already being in use!
> 
> Thusfar, I see two things:
> 
> (1) years of history has shown that non-atomic readq/writeq on 32-bit 
> platforms has been sufficient, based on testing and experience.  In 
> fact, in niu's case, a common readq/writeq would have PREVENTED a bug.
> 
> (2) unspecified fears continue to linger about non-atomicity
> 
> We should not base decisions on fear, particularly when the weight of 
> evidence and experience points in the other direction.
> 

I have personally dealt with at least one device who'd want to opt out
of a standard readq/writeq (it's not in-tree because it never shipped,
unfortunately.)  Doing the opt-in headers seems like a reasonable thing
to do to me, but perhaps I'm just being overly paranoid.

	-hpa

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