linux-kernel - Re: [PATCH 09/10] x86-32: use SSE for atomic64

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Message-ID: <ff13bc9a1002181049v2605b442y9f33008548b58d48@mail.gmail.com>
Date:	Thu, 18 Feb 2010 19:49:41 +0100
From:	Luca Barbieri <luca@...a-barbieri.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andi Kleen <andi@...stfloor.org>, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/10] x86-32: use SSE for atomic64_read/set if available

> This really sounds like the wrong optimization.  These functions aren't
> exactly all that complex in assembly (which would also allow them to be
> simple cli/do stuff/sti), and instead relying on gcc features which may
> or may not be well supported on x86 is inviting breakage down the line.
>
> That is particularly damaging, since the remaining 486-class users tend
> to be deeply embedded and thus we only find problems later.

There is the downside of adding a whole 386/486-specific implementation.

It's not too hard though, and if we don't care about 486 SMP, it may
be a better option.
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