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Date: Mon, 14 Jan 2002 07:12:26 +1100
From: Peter Jeremy <peter.jeremy@alcatel.com.au>
Subject: Re: Request for review: getcontext, setcontext, etc
In-reply-to: <20020111145159.N7984@elvis.mu.org>; from bright@mu.org on Fri,
 Jan 11, 2002 at 02:51:59PM -0800
To: Alfred Perlstein <bright@mu.org>
Cc: Nate Williams <nate@yogotech.com>,
	Bakul Shah <bakul@bitblocks.com>, Dan Eischen <eischen@vigrid.com>,
	arch@FreeBSD.ORG
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On 2002-Jan-11 14:51:59 -0800, Alfred Perlstein <bright@mu.org> wrote:
>* Nate Williams <nate@yogotech.com> [020111 14:46] wrote:
>> 
>> The point is that this may not be a valid assumption w/regard to the FPU
>> state.  The necessity of saving/restoring the FPU state *IS* the primary
>> subject of the the entire discussion, with the secondary part being that
>> x86 hardware is broken, so it may not be possible to guarantee delivery
>> of FPU exceptions to the same context that caused it.
>
>Couldn't this just be simply done by calling the "wait for fop to
>complete" instruction before switching out an FP using thread?

Given the current implementation (lazy FPU context load), if the
thread hadn't previously use FP, then issuing an fwait will cause a
"device not available" trap to the kernel.

Peter

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