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Date: Sat, 3 Mar 2007 08:19:33 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Davide Libenzi <davidel@xmailserver.org>
Cc: Nicholas Miell <nmiell@comcast.net>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Arjan van de Ven <arjan@infradead.org>,
       Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3
Message-ID: <20070303071933.GA2241@elte.hu>
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* Davide Libenzi <davidel@xmailserver.org> wrote:

> [...] Status word and control bits should not be changed from 
> underneath userspace AFAIK. [...]

Note that the control bits do not just magically change during normal 
FPU use. It's a bit like sys_setsid()/iopl/etc., it makes little sense 
to change those per-thread anyway. This is a non-issue anyway - what is 
important is that the big bulk of 512 (or more) bytes of FPU state /are/ 
callee-saved (both on 32-bit and on 64-bit), hence there's no need to 
unlazy anything or to do expensive FPU state saves or other FPU juggling 
around threadlet (or even syslet) use.

	Ingo