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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87eikj54wp.fsf@basil.nowhere.org>
Date:	Thu, 18 Feb 2010 09:23:02 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Luca Barbieri <luca@...a-barbieri.com>
Cc:	mingo@...e.hu, hpa@...or.com, 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

Luca Barbieri <luca@...a-barbieri.com> writes:

> This patch uses SSE movlps to perform 64-bit atomic reads and writes.

You seem to have forgotten to add benchmark results that show this is
actually worth while? And is there really any user on 32bit
that needs 64bit atomic_t?

I have to agree with Peter on it being a bad idea very likely
to mess with FPU state like this.

I'm also suspicious of your use of global register variables.
This means they won't be saved on entry/exit of the functions.
Does that really work?

It's also a not widely used gcc feature and those are always
somewhat risky.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/