linux-kernel - Re: [patch 06/11] syslets: core, documentation

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Message-ID: <Pine.LNX.4.64.0702141452240.7796@alien.or.mcafeemobile.com>
Date:	Wed, 14 Feb 2007 15:17:59 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Benjamin LaHaise <bcrl@...ck.org>
cc:	Russell King <rmk+lkml@....linux.org.uk>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ulrich Drepper <drepper@...hat.com>,
	Zach Brown <zach.brown@...cle.com>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 06/11] syslets: core, documentation

On Wed, 14 Feb 2007, Benjamin LaHaise wrote:

> On Wed, Feb 14, 2007 at 01:06:59PM -0800, Davide Libenzi wrote:
> > Bear with me Ben, and let's follow this up :) If you are in the middle of 
> > an MMX copy operation, inside the syscall, you are:
> > 
> > - Userspace, on task A, calls sys_async_exec
> > 
> > - Userspace in _not_ doing any MMX stuff before the call
> 
> That's an incorrect assumption.  Every task/thread in the system has FPU 
> state associated with it, in part due to the fact that glibc has to change 
> some of the rounding mode bits, making them different than the default from 
> a freshly initialized state.

IMO I still belive this is not a huge problem. FPU state propagation/copy 
can be done in a clever way, once we detect the in-async condition.



- Davide


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